Root on A string
x466xx
C♯5 is the C♯ power chord. Its notes are C♯ and G♯. It is the same chord as D♭5. No third means no major or minor quality. Mute unused strings carefully.
x466xx
9-11-11-x-x-x
Numbers show frets from the low E string to the high e string; x means don't play that string.
Every C♯ and G♯ on the first 12 frets. The filled dots are the root, C♯. Build your own shape from any nearby group.
Other C♯ chords
Other power chords