Access to the Administration -> Resources tab and find the resource you want to associate.
For each resource, on the left side of the ‘i’ icon, a handcuff icon can be found. When the handcuff is crossed out, the resource is already associated; when the handcuff is open, it is not yet associated.
To associate a resource, simply click on the open handcuff and a window appears, then enter the reference number of the sensor to be associated and that's it.