I'm using Finale Notepad 2012 to transcribe a piece, and there is a clef change in the beginning of a measure.
I can't find the clef tool that everyone seems to be referring to. Is there some other way to change the clef?

I don't think that's possible on Finale Notepad. You probably have to upgrade to PrintMusic, at least.
Try Finale Songwriter if you can.

If Finale Notepad allows you to have more than 2 files open at the same time, try to open this (done with Finale 2011) and copy-paste the clef to the other file.

You can also work around with MuseScore which is similarly free. Create the blank score in MS with all the clefs marked in, save as musicXML and import into Notepad. A little copy-pasta of the stuff you've already written and you are all good (can result in weird formatting occasionally, so you might have to tweak).

You can also work around with MuseScore which is similarly free. Create the blank score in MS with all the clefs marked in, save as musicXML and import into Notepad. A little copy-pasta of the stuff you've already written and you are all good (can result in weird formatting occasionally, so you might have to tweak).

Or just use MuseScore to begin with, considering it has at least twice the functionality of Finale Notepad and is 100% open source and free. I really don't get why people continue to torture themselves with Finale Notepad, it's like cancer..