Go to Settings (Cogwheel) at the top right and click on Links and then click on the Add button.
Select Exact Online.
Select the country of your administrations (Belgium, Germany, Spain, The Netherlands).
Give a recognizable description to the link with Exact Online and click on Next.
Click Finish. You will be directed to the webpage of Exact Online. Log on to this page, the link will be finalised, and you will be redirected to TriFact365.
Make sure the link is made with an Exact Online User with sufficient rights for the administration(s) in Exact Online to work with in TriFact365.