All contests have some sort of report, mostly the signal report then additional pieces of information, from your age to your shoe size (seriously).
Here’s me on 15m during IOTA 2017:
(100 Watts, recorded straight out the TS590SG into Audacity)
Antenna: DX Commander Vertical 80m-10m
For UK mainland, you would give something like this:
> Report > Ser Number > EU5
You’ll note that the report is most often 59 (although feel free to give a genuine report if you fancy it) then a serial number and finally your Island.
You can search for your island here: https://www.rsgbiota.org/info/advanced_search.php