1. Thread the ail of yarn onto a tapestry needle.
2. On the wrong side of the crocheted fabric, take the needle, from bottom to top, behind the first loop of yarn on the upper edge.
3. Pull the yarn through.
4. take the needle behind the second loop of yarn on the upper edge.
5. pull the yarn through as before. Weave the yarn through several more loops in the same manner.
6. Trim the excess yarn close to the fabric.
Note: if you don't have a tapestry needle, you can use your hook and basically do a slip stitch to weave the tail of the yarn.