Assignment of Dimensions to Characteristics in PLOB

Hi APO DP Experts

I am in transaction /SAPAPO/MSDP_ADMIN, trying to create Planning Object Structure. I copied chracteristics to the PLOB. All of them show Dimension 1.

I would like to assign Dimension 1,2, 3 to Customer, Product and Country for example. When I click on 'create dimension' button nothing happens. How do I get to create/select dimensions?

Thanks in advance and any help is greatly appreciated

Anton