How exactly do you use email aliases?

I've made a few alias addresses (not external/custom domains), under the assumption that each of them would have their own inbox that I can switch to. But I can't figure out how to use them, beyond creating and deleting them, and I can't view the emails that are sent to my aliases.

The mailbox's Knowledge Base only tells me how aliases work and how to create and delete them.

Any help or guide as to how I can manage aliases in Portal?