Remove the left lower cowl and the coolant overflow tank is just under the frame spar.
Check the coolant level with the bike upright. Don't over fill.
To add coolant, you need to not only remove both lower cowls, but the upper cowl as well.
I have no idea why Honda put the radiator cap under the right-rear part of the upper cowl.
If they could just have moved the neck a few inches to the rear or made a cutout for access it would be no problem. But no.
Be sure and check your hose clamps to ensure they're snug, especially the left radiator hose clamp as it is notorious for leaking.