How to attach garland to table’s edge?

You could probably tape the table cloth to the table with doublestick tape (or regular tape) on the opposite side of the table. Then the garland could use long twist ties to go around the garland but then tape the ties to the table cloth. or use pins or safety pins to hold the ties to the table cloth.

Venues should have tablecloth clips you can borrow. Or you can purchase these easily and attach zip ties to allow the garland to hang the way you want.