To associate the catalog of a group with an optician, it must first be created in iWiCatalog.
In the Groupment tab of the Parameters section, create a new groupment (see screenshot above).

Make a publication so that the addition, modification or deletion of the Groupment is operational.

As a result, if you access to your opticians' customer profile in Order Entry, you will find in the General tab, the groupments present in Customer Profile drop-down list.

Do not forget to Save when you consider that you have completed your modifications.