For manual upload, you could use an ftp program like FileZilla https://filezilla-project.org 

Upload the unzipped folder-app to modules > boonex (if it is a boonex app), or upload to just modules if it is from some other vendor.

Next, it should show up in Studio under apps > downloaded, ready to be installed.

That is how normally apps are installed manually, but some vendors might have special instructions for their apps, you could check with the app owner.