Aye, watch the Stans vids..
The two tricky but important bits are getting the bead to pop on, then the sloshing fluid round to get a good seal.
There’s a few tricks..
To get the bead on put a tube in it for a day or two to stretch the tyre/bead into the right shape.
If the tyre is tight to get onto the rim initially put both beads into the centre bit of the inside of the rim, that helps.
Take a bit of the bead off the put the sealant in (or use a valve with a removable core and inject) pop the bead back in (tight) then pump like mad- it won’t seal properly (probably) the first time but its just to get the bead back on.
Then the turning, shaking and flipping. Followed by more rapid pumping up.. After enough of the shaking and flipping it should stay airtight- enough of the fluid should seal it and leave some excess for sealing punctures. If you get air bubbles or hear leaks just repeat the shaking turning and flipping.
The first time I did it it seemed a right pita but after that it gets easier the more you do it.
I had a leaking valve seal so had to do it a coupla times before a bridged valve from an old inner tube solved it.
Since then its been great!