If you are introducing a menu as a waiter at a Chinese restaurant, how would you say for 主菜, we serve 北京烤鸭, 点心, and 四川火锅? I started learning Chinese about three months ago.

If you are ordering from a menu, you just say wo de (food items). If I am introducing entree options, how would I say that we serve 北京烤鸭, 点心, and 四川火锅?
If I'm understanding the question correctly, you are asking from a waiter's perspective how would you say we serve 北京烤鸭, 点心, and 四川火锅? 

There are many ways to say this. The easiest is probably "我们有北京烤鸭、点心和四川火锅"

Note that 点心 sounds a little weird in this context since it's usually perceived as dessert, not an entree item. So I would say "我们有北京烤鸭、四川火锅和餐后点心"

You mentioned saying "wo de (food items)" to order, but this is not a correct sentence to me. You might want to say "我想要..." "我要..."

Also, as an unrelated note, it's very rare that a restaurant would serve both hot pot and peking duck, since hot pot restaurants usually have tables specifically designed for their hot pots.