Don't know how to press flaps properly

Hi Guys! I'm an absolute beginner on guitar and just starting to learn. i've got problem here. I need to play chord that need to press the flaps but not sure which is the correct way to press. I'll try and explain below:

1) i need to pick open string C(5th string on 3rd flap) 1st
2) after that i to play all F(1st string on 1st flap), C(2nd string on 1st flap) and A(3rd string on 2nd flap) notes together.

Now im encounter the 2nd part a very big problem. How in the word do i press F and C on the 1st flap? Do i use my no 1 finger and hold the 1st 2 strings on the 1st flap and 3rd finger on A and strum all 3 string together? I feel that what i've done is wrong and there must be an easier way to play C and then play F,C, and A together. I hope you guys understand what im trying to say and could teach me the correct or easier way to press the strings i want above.

Don't be surprise if i ask more of this questions in the future because im a total noob playing a guitar now. Thanks!

nothing like getting to grips with some good old flaps :D

Flaps = FRETS
And yes you do use your first finger to hold down the two high strings on the first fret
OR
You can use Barre chords - where your first finger is pressed down across all six strings.