come aboard
and go aboardto get onto a boat or ship. Please come aboard. We are shoving off now. Please ask everyone to go aboard.
get aboard something
to get onto a ship, a train, or an airplane. What time should we get aboard the ship? Everyone can get aboard at noon.
take someone or something aboard
to load someone or something onto a ship. The ship was in its berth, taking passengers aboard. The ship took many tons of cargo aboard.
Welcome aboard.
Fig. Welcome to employment at our company. (See also on board. Invariably said in greeting to a new employee.) Glad to meet you. Welcome aboard.