Custom PHP

I do not know php. Yet somehow I have created a MYSQL database with some data in it that I can call with php. It’s all very rudimentary, but it works.

I would like to fold this into my WP theme. The question is how.

I created a custom page template and put the code in there. That didn’t seem to work.

I suppose I could use an iframe, but it seems that there should be a better way.

Any thoughts (and handholding) is welcomed.