How do I mark a measure in the music notation program PriMus?

I'm working on a laptop with the free version

Add

Right click on bar line -> insert empty bars…
"add" (= piece -> add measure)
Piece -> Add bars

Remove
Last, empty bar: remove (= piece -> cut bar)
or else always:

Click on "Selection Grades" at the bottom so that there's "Selection Bar" (if not already done)
select the measures to be deleted by pressing CTRL + click
Selection -> Delete -> Bars