The official list of members can be found here.
Only add this userbox if you are indeed a member on that list. Otherwise if you're just active in community, addinstead
By including this template in your user page you are added to the category Official_members_of_OpenStreetMap_Belgium.
Simply addto your page.
(Your name will also be shown in the general list of community members. No need to add the community userbox as well)