Let it grow!
Let it get to looking like this:
View attachment 124649
Or maybe even longer before you cut back.
Don't pinch it back.
Olives, when they extend new shoots, tend to send out two side leaves, and one bottom leaf. Once it builds up a head of steam of new growth, you can pull off the bottom leaves. Then, later, you can cut back. When you do, the new shoots will come from the two remaining side leaves, and not the bottom of the branch.
When you cut back, it will look something like this:
View attachment 124650
I've also wired the new shoots. Using aluminum. The wire doesn't stay on very long if it's growing. Maybe two months at most.
Olives develop ramification very quickly!