I havent' used Print Music much, but:

You should have a "User's Manual" installed with it, that will come up if you click Help in Print Music. Select the Users Manual, which is a .pdf file. You can use "Edit - Find" in the Manual to search, and most of the index is linked to "jump" you to the applicable page.

To delete a measure you have to select it with the "Mass Mover" tool - looks like a little train engine. Click on the engine to get the tool, select the measure(s) you want to get rid of, and then -
a) to delete the notes and rests in the measure so that you can put something else in, hit the Backspace button.
b) to delete the measure entirely, and remove it from the score, hit the Delete key.

Or so it says...

John