You can see the ORB AN ports here.
This gasket is very similar to a head gasket. It seals the two halves of the tank.
These seven bolts fasten the two halves together. Anti-seize compound is used as an assembly lube here, similar to using “real” assembly lube on cylinder head bolts. Anyone who’s used anti-seize knows it somehow gets EVERYWHERE. I’ve found the best way to not make a mess is to put a dab of anti-seize onto a paper towel and simply dip the end of each fastener into it, like in the picture.
Next, put the two halves together, and begin to gradually tighten the bolts in a crisscross sequence (again, just like a cylinder head).
Torque each of the 3mm Allen bolts to 50 in-lb.
Now install the sight tube. These brass elbows already have Teflon on the threads. Tighten them by hand, then use an 8-mm wrench to put an additional 2-3 turns on them.