how do you make your background transparent

To make the bottom layer trasparent you need to change it from being a backround layer to being an ordinary layer. Click on the lock symbol next to the layer in the layers panel. You will then be able to erase all or parts of it.

You will also need to save in a format that supports transparency e.g. PNG, TIFF or PSD. Jpeg does not support transparency.

Dave

In Photoshop....

Let's say that you created a new document or project. 

You will have a white background layer by default.  Create a new layer, then erase the white background layer.  Then you will have a transparent background.