Your artist will arrive 1 hour before your guests, which is 2 hours before they play (they’ll contact you otherwise), this gives them time to set up, warm up and relax.
When your artist arrives, show them where they’ll be playing and offer them something to eat/drink. Show them to their ‘Green Room’ (Just a spare bedroom/office type situation), it’s somewhere to leave their things and warm up away from your guests. It’s a nice gesture to leave some nibbles and something to drink in the ‘Green Room’ too. Make your artist feel at home!