Begin with a crochet hook and a length of yarn folded in half (Photo 1).
With the WS of the knitted fabric facing, insert the hook into fabric, where desired, from front to back (Photo 2).
Pull the folded end of the length of yarn through the knittied fabric (Photo 3).
Insert the tail ends of the length of yarn through the loop (Photo 4).
Pull tight (Photo 5).
Turn to the RS to see it completed (Photo 6).
Try out adding fringe:
Here are a free pattern where you can try out adding fringe:
• Provence Striped Top