你和我一起去。 You and I go together.
他和你一起去。 He and you go together.
A、B和C一起去。 A, B and C go together.
我们/你们/他们 一起去。We/You/They go together.
So basically if you want to specify that there are more than one subjects in your sentence, you use 和 to connect them, and put the word 一起 before their action.
Hope this will help you.