At the beginning of the round, you're chaining 3. Then you go around. When you get to the end of the round, you will slip stitch to join. They want you to place the slip stitch in the proper place. If you join in the chain, it will look funny. Look at the stitches. The chain will be vertical. Count up three stitches and place your hook into the fourth. It will be sitting at the top of the work and will be horizontal. You'll know it's the proper stitch because it will have two loops for you to slide your hook under. This is where you should join. After you join, you chain 3 again. This brings your work up to the proper height so you can continue on the next round. I hope this makes sense to you.
Welsh corgis are cool.