I have some excel password protected workbooks. How do I get enpass to be able to open them?

How do you get Enpass to open a beer for you?

Not sure if you're referring to WebApp-version of Excel or fat client, but im guessing an locally installed app.

What you're after is AutoType, something i miss very much in Enpass and hence do not use enpass as my daily driver.

AutoType like applied in Keepass,keepassxc or Keeweb doesn't rely on any extra plugins to autofill but simplified acts like a keyboard and types the value in the textbox in focus atm.

Enpass can't do that now so you'll have to rely on the Clipboard-feature. Watch out for clipboardhistory though.