Graph Editor

We've got the main 16 poses framed but now we need to cycle it so no matter how long the animation is, it'll still be moving. Start by selecting all of the rig's controls and open out the Graph Editor. Then go to View and check "Infinity".

For now, the graph will look something like this where there is a flat linear line before and after the animation. To achieve a cycle go to Curves > Pre Infinity > Cycle. Then Curves > Post Infinity > Cycle. 

Your graph should look like this, where the keys are repeated before it's first frame and after it's last. This is why we needed the first and last frames to be the exact same, so there is a smooth transition when cycling. After, go to View and check "Show Buffer Curves" this is another useful tool which displays the original  shape of the curve after we edit them.