When your on your account you have your profile picture, right? Well right next to it is a little camera thingy so when you tap that it will allow you to change your profile picture. Hopefully this helps!

I have been trying that, but it says Pic Collage isn't hooked up to my photos

You may have to allow it to access your photos.

I Reyes, but I doesn't pop up in my settings

did instead of Reyes