The simplest approach is to cut off the picture part, punch a hole, add a string or ribbon and tie it onto the gift. I always like to use bakers twine, it has that nice red and white candy cane look to it and yes I do save it from things I get from the bakery.
If you want to get a little fancier you can use a tag shaped punch which you can get at most craft stores.
Punch out as many tags as you can from the card, punch a hole and add a string or ribbon.
These projects are simple and fun to do with kids during the holidays.
Have a fun day!