Can I just use a normal click or does one have to use drums?
If you just want to use the metronome, follow Gregs advise above. I for some reason thought you wanted a different sound. But yes, you could use any sound or sample you want to really.
So the mapped out tempo changes will be remembered?
Yes, again, The tutorials Greg provided a link to, as well as the section of the Mixcraft manual in my link should explain the use of markers for tempo changes. Experiment with it a bit and you should pick it up quickly.
Personally, if I were looking to set up a song, especially a song with multiple tempo changes, I would try to use some kind of drum or rhythm track with some kind of "fills" or some way of signaling the upcoming tempo change. It could be a scratch track to be replaced by a more "finished" drum track later in the project developement or something along those lines.