I'll have to read up on bleating the thermostat housing first.
Not much too it. Take off the radiator cap and fill the system to the brim, rock the bike side to side to "burp" the system, top it off if necessary, and put the cap back on. Fill the reservoir half way and start it up. After it's started to warm, open the bleeder on the thermostat a turn or so until water flows (not spitting). Close the bleeder. Let the bike warm up; I wait until the fan comes on. Then, let it cool off and adjust the level in the reservoir if necessary.
I'm guessing you're suggesting the one in the middle and mix it 50/50 with distilled water. Right?
Right, or, pay more for the already diluted stuff.
 Zerex G05 and ZXG051 are the same thing. ZX = Zerex, G05 = G05 and 1 = 1 gallon. ZXG05RU1 is the same thing diluted 50/50, R
eady to U
Should I flush out the old coolant first or is it fine to just add this new product?
It depends. If the coolant is more than a year or so old, I'd drain it all out. You can stick a garden hose in the top and let it run out the two drain plugs for a while if you want. Then, refill it with clean 50/50 mix.
You mentioned to check the level after the bike is cold. Does that mean I should warm up the bike before topping off the coolant (after bleeding the thermostat housing first)
Yes. fill it, bleed it, run it up to temp (bleed again) then allow it to cool completely before adjusting the level. The thermostat housing should be full to the brim and the reservoir just above the lower line.
When the system heats up the coolant expands and the excess is forced out through the cap into the reservoir. When it cools off it sucks coolant back in from the reservoir as the coolant contracts (shrinks?)