Building blocks and document properties

Hi there,

We are using the Category document property to store our company confidential classification. This is a defined set of options.

We have created building blocks for each option, but cannot work out how to assign these to the property.

We don’t want our team to be able to type anything they want in here, but be restricted to those options.

Does anyone have any advice as to how we can achieve this please?

Cheers in advance