How can I use my signature, which is now a jpeg on white background, on different backgrounds?

Sorry, Lisa, you can't afford me.  😁

If you want to attach your signature file here, I'll see what I can do for you.

@default7in4kiwgguuc, I don't know what option you are trying to access.  If you are talking about my suggestion to create a brush, please review the video tutorial that I linked.  It explains everything in detail.

Another useful way to perform this task on multiple images is to create a brush out of your signature.

• Use the magic wand tool to select your black signature (on a white background)
• Under the Edit menu, choose Define Brush from Selection
• In the pop-up dialog, give your signature brush a name.

Your signature brush will now be available for adding to any new file.  This makes your signature very flexible.  For example, you can resize it, using the square bracket keys.  You can add it to a new layer, change the color and opacity, and add various styles it.

For further details, here is a good video tutorial.

Change the Layer Blending Mode of the Signature layer to Multiply.