In Beginner mode, new ships come pre-equipped with all the essentials, thought they can still be customized. In Intermediate mode, new ships are spaceworthy but lack specialized components needed to complete missions. Ships created by Experts are just empty cans, and must be outfitted completely by hand. The systems available range from the big stuff like Warp Drives and Shuttlecraft to the generally unseen gizmos like power distribution networks, sensor pallets, subspace radios and replicators. Weapons, shields and probes must also be chosen, as well as the style of living quarters, which affects the size of crew the ship will carry.
Success depends on if the ship is properly outfitted and how suited the crew is to their positions.
Once the new ship is complete, it's time to pick your command crew from a long list of candidates. The list varies depending on what era your starship comes from. Constitution or Excelsior Class ships can be crewed by Classic Trek folks, while the others draw on Next Generation and later officers. But this makes selecting the crew interesting since it forces you to draw on the more obscure but often quite interesting Starfleet folk such as Barclay or Rachel Garrett, captain of the Enterprise-C . Then break the champaign and cut the ribbon, your ship is finished.