I would echo what @TheNumberOfGeese@feddit.uk said about a hire place giving you an introduction on the basics. You should insist that.

Canal & River Trust Boater’s handbook is a a good place to start. They also have a bunch of Youtube videos that’ll prepare you well.

Here are a few random suggestions based on my mistakes and experiences:

• don’t try to cover too much distance per day
• cruise really slow and you’ll enjoy more
• too high boat speed is a recipe for mayhem
• locks may seem scary at first, but they are really easy so long you don’t let water in too fast too quickly
• help others at the locks and you’ll have nice chats as a bonus
• the boat really does not steer unless there is propulsion
• try to learn to use steering and propulsion as gently as you can; shouldn’t take much practicing
• reverse gently if you beech your boat, and if that doesn’t help, the long pole is your friend (also very useful when your boat ends up stuck across the canal!)
• if you are into slow cooking, lamb/beef/vege stew gently bubbling during the day as you cruise is heaven