Well, as far as getting up there, you really have no choice other than to push it up, or motor it up gently, but 350lbs is getting to the max of being able to do that. I've used those type carriers for my DR650 which is just shy of 350lbs and it was a bit of a handful, but doable. My scooter that I used was much lighter and of no consequence. Depending on your physical ability, will determine whether you will be able to do this. You must have one of the larger cc type scooters.
You might be able to "motor" it up, but that takes very precise control of the throttle, and depending on how tall you are, and how tall the carrier is you might want to consider a step stool to transition up onto once the bike gets up on the carrier. A second person is ALWAYS a good idea, even if you have to recruit someone.
2014 Newmar Ventana 3634
Cruiserlift Motorcycle Lift carrying a 08 Yamaha FJR1300
Toad = 2008 Dodge Dakota carrying Suzuki DR650