Good work on the purchase, what a strange setup for that frame though, takes all sorts!
For fitting a tight tube, I would:
Fit one side of the tyre bead inside the rim
Apply loads of talc/chalk to the tube to stop it sticking inside the tyre/rim
Carefully fit the tube within the tyre, no twists
Inflate the tube a small amount, just so it takes shape
Wet the rim and bead that isn't seated and squeeze on with thumbs, no levers! 2x people here can help too. Squirt some more water if needed to help the bead slide over the rim.
Good work on the purchase, what a strange setup for that frame though, takes all sorts!
For fitting a tight tube, I would:
Fit one side of the tyre bead inside the rim
Apply loads of talc/chalk to the tube to stop it sticking inside the tyre/rim
Carefully fit the tube within the tyre, no twists
Inflate the tube a small amount, just so it takes shape
Wet the rim and bead that isn't seated and squeeze on with thumbs, no levers! 2x people here can help too. Squirt some more water if needed to help the bead slide over the rim.