Working out how the tavern functions in Manor Lords is an important step in caring for your families. Tavern supply is one of the listed amenities alongside church access and water supply, so it's a necessary provision if you want to upgrade your burgage plots to level three. This will let you collect more regional wealth from them per month, but more importantly, is a condition for becoming a large town.
That said, this isn't your bog standard city builder where you can just build a thing and it'll function perfectly. In order for your tavern to provide access to your subjects, you'll also need to procure the ale that gets served there. Here I'll explain how the tavern functions, plus the different ways you can get ale and provide access.
Unlike the church, where you can provide access simply by building it, for the tavern to work properly you'll need to supply it with one all-important resource: ale. After all, it's not much of a tavern if there's nothing to drink. There are two main ways you can get ale.
The first is to make it yourself:
That's for sure the most complicated method. If you have surplus regional wealth through trade, you can use the cheap and nasty solution:
It's worth noting that you can import barley and malt, too, and these are cheaper than directly buying ale, so you might choose just to skip a couple of steps in the process. Since you only need tavern supply at the point of upgrading your burgage plots to level three, I'd suggest having the resources ready to upgrade all of them before you import your ale, then you don't need to worry about constantly supplying your tavern while you accumulate the rest.