"I ride the bus."
Yes, but that sentence uses the verb 行きます "go", not the verb 乗ります "ride". What Ruveyda was trying to say is that when you use the verb 乗ります, the vehicle is marked by に (but we don't need to add "in" in English, since the English verb can be used transitively). The fact that, when using 行きます, the vehicle is instead marked by で in no way invalidates this.
This is correct, not sure why people are downvoting.
In English, "ride" is a transitive verb, meaning it takes a direct object. I ride what? I ride the bus.
In Japanese, 乗ります (norimasu) is an intransitive verb. It can't take a direct object. Direct objects are marked with を, but since this verb can't take a direct object, you can't use を. Instead of "I ride the bus" it's more like saying "I ride in the bus". To mark the indirect object (I ride in what? I ride in the bus), you use the particle に:
Basu ni norimasu.