In this article, I’ll show you how to upgrade the latest WSP file to an existing file on Farm Solution in a few simple clicks.
You can save the WSP file in any folder.
Open SharePoint PowerShell and run it as administrator; then run the following script:
Install-SPSolution -Identity <File Name> -WebApplication <URL>
Give it a moment, then go to Central Admin->System Settings->Manage Form Solutions.
We can see the Bamboo.CalendarPlus.wsp file upgraded on it.