How do I cook frozen spaghetti?

Cooked a bunch of spaghetti and sauce last week. After a day or two I spooned the leftovers in a freezer bag and popped it in the freezer [sauce mixed in with spaghetti noodles]. Now I'm not sure how to defrost/cook it so that's it edible again. Can I throw the bag in a pot of water and boil it? Do I let it thaw in the fridge and wait to microwave it in serving sizes? Thanks