I'm not getting Copy and Paste

This is going to look so basic that I feel rather embarrassed in asking it, but I can’t get Copy and Paste to work as I expect, and it’s to do with voices. If I copy a bar in one voice and paste it into another bar where there’s already material in the same voice, all well and good. But if there’s another voice in the destination bar, its music for that bar stays put. How do I paste in such a way that all the material in the destination bar is replaced? Sorry about this.

Paste whole bars (or groups of bars) or clear the destination bars before you paste.

Thanks, pianoleo. The second of those certainly works, so I’ll stick with that, as I’m still having no success with the first.