Learn Swedish: Du får gå hem nu. - You may go home now.

The verb får is used to express permission, meaning "may" or "are allowed to". If you used kan instead (Du kan gå hem nu), it would sound more like you simply have the physical ability or opportunity to go home, rather than being granted permission.

Why is there no att (to) before gå?

Because får is a modal verb. Just like in English where we say "You may go" instead of "You may to go", Swedish modal verbs are followed directly by the dictionary form of the next verb (the bare infinitive), without using the word att.

I've seen the word hemma for "home". Why is it just hem here?

Swedish distinguishes between being at a location and moving toward it. You use hem when there is movement toward your home, like in this sentence with gå (to go). You use hemma when there is no movement and you are already located at home.

Does gå mean "to go" or "to walk"?

It can mean both! The phrase gå hem translates naturally to "go home". However, depending on the context, it can also specifically mean "walk home". If you wanted to specify traveling by a vehicle, you would use a verb like åka (to travel/go by vehicle) or köra (to drive) instead of gå.