Starting a score "mid-measure" without rests

Hi

I wondered how I can start a score mid-measure without the system automatically adding rests to fill up the quantity required for that measure?

E.g. "O Come All Ye Faithful" starts on the 4th count of the first bar with a quarter note or "If You're Happy & You Know It" starts on the 4th count with an eighth note.

Probably a very simple solution, but I can't work it out.

Please help!
Thanks