I’d suggest doing it clipped in from the start, otherwise you’re just putting another barrier in front of you.
Best place to start is in a door frame, you can get yourself set up static with an elbow or a hand for initial support. If it all goes wrong you won’t move far in either direction.
You want your front hub an inch or so behind the centre of the front drum. Make sure your tyres are nice and firm, soft tyres make it all much harder.
It’ll feel weird to begin with, but a steady, brisk cadence is everything. Use your hand to balance and work on pedalling steadily so your upper body is upright rather than leaning into your support. The quicker your cadence the steadier you’ll be.
Work towards taking your other hand off the bars and moving your centre of gravity back so you’re sitting upright, while still supporting yourself. This will let you feel how stable the bike is when your cadence is good, your upper body’s relaxed and you’re looking forward.
The final hurdle is moving that supporting hand onto the bars so you now have both hands on the bars with no support, that’ll feel scary to begin with and might take a little while! Just keep the cadence up and you’ll be fine. Any wobbles, pedal faster!
Day two, set them up in the kitchen next to the oven and make an omelette while pedalling.