I'll try to make a simpler answer for you.
Everyone else is right, but confusing depending on your level of play.
Say the song is in F. You enjoy playing D shapes and the associated G's, Em's A's etc.
Place the capo on the third fret, near the fret bar. When you play a D shape, that will correspond with, say, your bass player playing in F.
Your G shape will actually be a Bb, your Em shape will be an actual Gm, your A shape will be a CMaj, etc.
If you want to use D shapes in the key of C, yeah, you'll have to capo way up on the tenth fret.
For songs in A, using a D shape, the seventh fret. Just to use your specific examples.
I like the capo myself, but tend to use it more often in alternate tunings. The Celtic tunings particularly lend themselves to those higher registers.
There are certain other chords in standard tuning, such as
that can be especially nice when capo-ed up, into say a C or A tune.