Ok, so I guess you haven't got it out on the road yet and warmed it up. Assuming for now that there's nothing wrong with the clutch, finding neutral when it's warm should be a lot easier. Oh, hang on, is it a wet or dry clutch on those Monsters? All that is for a wet clutch so ignore if it's dry! For a dry clutch, it sounds like "it's just had a new clutch" means either poor attention to stack height, etc or, as previous comments, possible slave-cylinder issues.
FWIW I can never find neutral on my 600ss (wet clutch) when the engine is running and I'm stationary - changes gear perfectly well but at rest neutral is elusive. If I remember when I'm coming to a halt I might be lucky and engage it whilst still moving, otherwise stop the engine and it's easy.
Ok, so possible slave-cylinder issues still a possibility and clutch-plate stack height issues apply equally to the wet clutch. Bleed the clutch first then try again, but really - it needs to be thoroughly warmed up to find neutral more easily. If you can get the rear wheel safely off the ground (engine off!) put it in, say, 3rd or 4th gear then pull in the clutch lever and try to rotate the rear wheel to get a feel of how much clutch drag you have. You'll need a friend for this! Alternatively just do the in gear thing (engine off) and push the bike with the clutch lever pulled in - you can still feel the clutch drag bit it's harder to judge...
