You will need to fly either a Licensing Proficiency Check (if the SEP Class Rating included in your licence hasn't yet expired) or a Licensing Skill Test (if it has).
Both are much the same - but we Examiners are supposed to conduct the LST in a more formal manner.
The test itself? Take off, climb, a couple of stalls, a couple of steep turns, about 20 min of navigation, a PFL, then back to the aerodrome for a circuit or few - one must be flapless and an EFATO is also required. All can be achieved in about an hour.
However, you will need to prepare yourself for the test, so do some dual training first.