UNA is complex on the first look only :-) After the short usage you will get how it is simple. About your trouble - here is the detailed manual about it https://github.com/unaio/una/wiki/Browseable-categories. Use the instructions from there till the header "Making select field browse-able" - that's enough for now, but you may continue to make it browseable.
Hello fatihaksoy!
UNA is complex on the first look only :-) After the short usage you will get how it is simple. About your trouble - here is the detailed manual about it https://github.com/unaio/una/wiki/Browseable-categories. Use the instructions from there till the header "Making select field browse-able" - that's enough for now, but you may continue to make it browseable.