I'm going to be showing you how to make your text flicker.
We'll just throw in a text layer with "hello" written in it. Make it white temporarily so you can see better. Then we'll go into "effects and presets", type in "glow" and drag the effect onto your text.
Then, to make it flicker, you'll go down into the text object's transform settings. Twirl down the opacity button, click "alter option", and then click the "opacity" button. This little thing comes up and type in wiggle. And this little thing comes up, just click enter. And then you could just mess with these numbers.
I think what I did was 50 and 100, then just preview that so much it does. If you don't like it, you could always change these numbers. If you want it to flicker more, you can do 100 and 200 or something. If you want less, you could obviously do less. But yeah, that's basically it.