So I'm brand new and I bought some Elixers because they can be used in battle. I just have one question. How do I put them in my bag so I can use it? When I go into my battle inventory they are not showing and I can't figure out why.

To use elixirs, you have to click "manage party", which is the red arrow .
From there, click "use item", select the elixir, click "view party", and select the pet you want to use it on.

Thank you. That seems odd, but whatever.