Form

Hi, I received a Fiche 281.5 form for 2020 from a belgian company i did mystery shopping assignments from online. I dont know exactly what it is but it gives the amount i earned which was 136 euro. How do i go about declaring and paying the tax on this? Is there some sort of online service i could use to sort it as i can never get my head around revenue site? I presume since they have sent me this that they have sent it to revenue although the form looks quite bare. My name and the amount earned are the only details filled in. I'm a regular paye worker and havent filed anything like this before. I havent done anything about getting the rebate for my pension plan etc in the last couple of years either as had no clue how to fill it in.