Himadri - It can be done in the way you suggested also - but why take the trouble ? most of the flight controllers can do this in easy way and in one step too !

I agree but on multiwii it require changing few lines of code and also knowing the endpoints!

No need to change many lines - only have to uncomment one line.
Also no need to know about end points - multiwii sets them at 1000 and 2000.

So I simply program the mwc fc and all the motors will start spinning??

It wont be that simple I am afraid.
First calibrate ESC with multiwii board - motor won't spin in this mode, however recommended to remove props.
Then upload Multiwii firmware with correct settings for your Setup.
then connect to PC and to check the receiver inputs and sensors are working fine, also calibrate both.
Set up flight mode switches and select arming procedure (Switch or <stick - default>) .
Now make sure there are no props on motors, connect battery arm the copter - give little throttle, and check motor responses to movements, in case of a tricopter, you have to make sure yaw mechanism is working as expected

Ohh..okay

Can somebody give me the link to multiwii firmware

Follow this Link :- https://code.google.com/p/multiwii/
to get the latest Multiwii firmware (v2.4) along with Multiwii configuration windows application.

Check this for ESC calibration : https://code.google.com/p/multiwii/wiki/ESCsCalibration

It may come out harsh but sorry to say that you havent done any kind of reading at all on how to assemble the product your were buying.
Moreover your choice of FC is gonna give you sleepless nights if you cannot figure out how PID's work. KK 2.xx or naza lite would have been a better option.
And above all you chose to go with a tricopter which is usually not suited for beginners in terms of assembling one.

Now, your copter looks fat! Have you weighed it? Each motor generates max 260-280gms of thrust @3s in testing conditions. You atleast need a 2.5:1 thrust to weight ratio to get a decent flight(2:1 gives you hover).

Anyways I had a tri with similar motors,fc,esc,lipo etc, and I would have shared the PID's but never saved them 
AUW was 350 gms and Flights werent too peppy but thats due to my preference.
Tri is partly dismantled, so will just put up pics of what remains, might be useful to you.

PS: the weight in image is not correct. frame+motors+esc+servo= 167gms approx

@side winder .. Sir I had done some search but couldn't understand much so I asked for help..and I will follow your instructions too.. Thank you 

Hello again,
Sorry I was off for some time, I had a question relating to the propellers
I had a syma x3 Quadcopter which had 4inch props.. But the problem is that the hole in the prop is a little small for it to fit on the motor
Question : can I increase the size of the hole of the prop cause I don't think I would be able to buy new ones until I am able to sell my 8 inch ones.. So can I do it?
(The props have three blades)

Please don't try any modifications with the props as it might prove to be dangerous however skilled or careful you maybe....better buy the correct props..
While trying to increase the hole diameter you may fatigue the prop 

I have some extra as I had got 8 of them ..so I can experiment .. how will I be able to do it?? Will I have to drill in and then in a circular motion enlarge the hole from inside? ?

However experiments with props are discouraged as they rotate at very high speed. It may also happen that your mod works but as soon as you increase the throttle the prop may break apart and the high speed bits can cause fatal injuries(think about the bit hitting you eye! Hope it never happens!) PLEASE AVOID SUCH EXPERIMENTS IN ORDER TO SAVE FEW BUCKS!!

Oh okay will remember that

Do I connect the esc and the motor by bullet connectors or directly solder them??

Its your choice!....there is no advantage of soldering it directly over connecting it with bullet connector! Some ppl prefer soldering some don't...the only advantage you'll get in using connectors is fast accessibility and you can quickly change a burnt esc or motor or swap wires! Even no need of cutting the heat shrinks!!!   

Himadri sir what do you prefer?

No Sir plz i am just 17!
I prefer soldering bullet connector...as it helps in quick access!

I am 3 years younger to you..so you are sir for me.. Thanx for the advice

@himadri having bullets helps reduce effort if you've wired the motor wrong and need to flip direction....

@aniket210696 i think i meant that only??

Nah you said there is no difference... Just saying

If your're skilled enough that should make no difference!