setting bpm for instrumentals using cubase

I have not used this software, and as no one has answered I offer the following. Time signature, aka, 3/4, 4/4, 6/8, etc. tells us how many beats per measure this song will use.
Once decided the song will normally use that time signature through out the song.

I would think the software would ask what time signature is to be used and then use that information to sub-divide the beats into measures.

Hope that helps.
 
I don't know what you mean. But in the transportbar (F2) you can type in the tempo of the song (for example 120 bpm) and if it's another measure than 4/4 you can change that too.

If you want to know the bpm of a cover song, just google it or play the song and put the metronome click on in the transportbar and listen if you have to fasten or slower the tempo.