[itsm] Linking items to customer

Hi, we're evaluating otrs::itsm, and so far is a great tool. One thing is not clear to me (for sure I'm dumb): how can I link multiple items to a customer? This to be able to get all items that a customer has, and to be able for the customer to select the item form customer panel while opening the request. I see that the links are defined under Core::LinkObject in sysconfig , but I can modify them, but not add. there's a way to do that, or the agent has to connect the item to the request every time a new ticket is opened? thanks a lot, Mat