So you mean the port shows up in the Tools > Port menu?
Which Arduino board do you have?
How did you have the power supply connected?
Please do this:
- File > Preferences > Show verbose output during: > compilation (uncheck) > upload (check) > OK
- Sketch > Upload
- After the upload fails you'll see a button on the right side of the orange bar "Copy error messages". Click that button.
- Paste the error messages in a reply here using code tags (</> button on the toolbar).