Odoo is the world's easiest all-in-one management software. It includes hundreds of business apps:
CRM | e-Commerce | Accounting | Inventory | PoS | Project management | MRP | etc.
First, you have to install MRP modules from Settings. Then, "Manufacturing" menu will appear at the top bar.
To set BoM (Bill of Material) simply go to Manufacturing -> Configuration -> Bill of Material Components -> Create the product BoM and its components. (Do not forget to tick Technical Features in User Access Rights)