Hopefully by the time you are reading this you know how to work into a chain already but are confused about the instruction to work into the "other side" of a chain.
Working into the other side of the foundation chain is common in modular and seamless crochet as it allows you to join and work in the other direction without having to sew pieces together. It can also be used for starting oval or rectangular pieces in the round, and often for the toes in toe up socks.
Once you've worked into the foundation chain once it will look like this. The arrows show each of the chains where you will work when you work into the other side.
To work into the other side of the foundation chain simply attach your yarn at the start of the row
Insert your hook exactly as you would for working into a chain.
Note that depending how you worked into your foundation chain you may have one strand, like I do, or two to put your hook under.
Then work along the row as instructed.
Sometimes the instruction to work into the other side of the foundation chain comes in the middle of the first round. This is the same principle as before
Work to the end of the chain.
You'll normally work multiple stitches into the final chain to allow there to be enough fabric created to move the piece around, as you work these stitches rotate the work in your hands
Continue to rotate, then work into the other side of the chain as directed.