This is my first playthrough so I very well may be missing things that are in plain sight. Anyways, my problem is I can't figure out how to mix Triss's potion and how continue mixing potions throughout the game. Can someone give me some pointers? Thanks!

No surprise, so many things to learn in the beginning. You will appreciate Geralt's journal: Ingame -> Press "J" -> Tutorial. Read anything about Alchemie / Meditation / Potions.

If you have all ingredients, go to the fireplace and click it to get into the meditation mode.

I think I have all the ingredients for my first potion. I just want to make sure how I'm supposed to mix everything together to make the potion. I'll check out the journal as you suggested. Thanks!

And, as it might not be totally obvious: You need to "rest" (i.e: meditate) to even get access to the potions window.