1. This should be quite straight forward.  If you have selected in the warehouse configuration Manufacturing "Pack and the manufacture", Odoo automatic create the routes, rules and locations you need.

On the product you want manufacture, select the manufacture route. A soon as a manufacture order is created, and internal transfer is created to pick components into manufacturing location. The locations are created automatic for you.

2. Operations are create also automatic for you, when you install Inventory app and manufacturing app.   I am not sure what you refer to as Actions in this context.  There are a lot of different type of actions in Odoo.

3. Work centers are linked to operation in Bill of material.  When a manufacturing order is created, this will create a work order for the work center in the manufacturing order.   A bill of material can have several operations on different work centers to complete the production of a material.