Transports are a little confusing. you just need to remember that loading AND/OR unloading uses all of the units movement points. This means that you can both load and unload a unit on your turn, or you can load a unit (granted it hasn’t been moved already this turn) and leave it on the transport, or you can unload a unit that is already on a transport; in this last case you would be unable to move it afterwards similarly to rules regarding movement before loading. I’m not sure if I helped clarify, but I hope this benefits you.