If you go to the left hand side of your timeline under the layer that you've applied your pins to and click the dropdown arrows next to your pins under Deform, you can reveal the keyframes:
Then, it's as simple as clicking and dragging on your timeline! Just click and drag to select the keyframes you'd like to manipulate:
After you selected the keyframes and they turn gold, just click and drag to move them around on the timeline.
I hope this helps! Let me know if you need further clarification! : )
Also, you can easily loop an animation in After Effects without having to copy and paste keyframes (which can get really tedious). Here's a tutorial on how to make an After Effects composition loop: