Coffee Mug Template [Topic edited for brevity]

What kind of file is the Template?

If it contains no layers, you might have a problem.

Can you show us a screenshot of your workspace with the layers panel open?

Nancy

When you state you want to design a coffee mug, do you mean you want to design the actual mug or produce a design to be printed onto a mug?

no, the template can come in a multitude of file formats. Photoshop can handle a lot of them. In what format (extension) do you have your template?

If Photoshop can handle that format natively, we can advice you on how to open the file. Most file formats are read into Photoshop on their own layer, except if you pass via File->open, where the data is probably read into the flat background layer, like with Jpeg. But also that one transforms into a separate layer, by double clicking the background in the layers palette.

I suggest you read this first: Learning layer basics in Photoshop