Learn Hardcore Afrikaans: Ek stel die instelling terug.

In a normal main clause, the finite verb goes in second position, so stel stays near the front, while the particle terug moves to the end:

Ek stel die instelling terug.

This is very common in Afrikaans and is similar to Dutch and German word order.

Is terugstel one verb or two separate words?

It is basically one verb, but in some sentence patterns it gets split.

In a main clause: Ek stel die instelling terug.
After a modal verb: Ek wil die instelling terugstel.
In a subordinate clause: ...dat ek die instelling terugstel.

So learners often need to think of terugstel as a single dictionary verb that may appear split in certain structures.

What does stel mean by itself?

By itself, stel can mean things like set, place, put, or sometimes state, depending on context.

In combinations, it often takes on a more specific meaning. Here:

stel = set
terug = back

So terugstel means reset or set back.