Visit AdminCP > Setup > Options > [MC] PC Builds. Set Maximum photos per build and Maximum photo file size, decide whether the postbit link should be available, and decide whether the PC Part Picker URL field should be enabled.
If you intend to monetise component links, configure Amazon affiliate links with your Associates tag. See affiliate links.
Navigate to AdminCP > Groups & permissions > Permissions and grant Manage own PC builds, Upload photos to own PC build, and View other users' PC builds to the appropriate groups. See permissions.