Hello @Estremadures0,
You may have done this already but make sure to carefully read any checkin instructions given by the host.
You say " in a building in which I MIGHT not have access in (keys)". If you're you saying "MIGHT" because the host said that then make sure to get exact instructions from them.
If the host's checkin instructions don't make this clear then make sure to ask them for the exact checkin procedure i.e. how to get the keys or code to the building, the keys or code to the listing etc.
Also make sure that you have the contact number for the host and put it in your phone's contacts list.
If the host doesn't respond then contact Airbnb support in advance of your trip. there should be contact information in the confirmation email the you received.
Steve.