come on board

Come on board means to join a group, organization, or effort.

The phrase borrows from the nautical sense of boarding a vessel—stepping onto a ship to become part of its crew.

In business and professional contexts, it describes joining a company or project: We're excited to have you come on board as our new director.

It can also mean adopting an idea or position: Once she understood the benefits, she came on board with the plan.