[otrs] Error while accessing "Customer User - Groups"

[Boniforti Flavio]

Hello list!
I get following error:

CustomerGroupSupport needs to be activ in Kernel/Config.pm, read more 
about this feature in the documentation. Take care!

How can I solve this?
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Boniforti Flavio
Provincia del Verbano-Cusio-Ossola
Ufficio Informatica

Tecnoparco del Lago Maggiore
Via dell'Industria, 25
28924 Verbania
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