OP, first I think it would be best to address the fear and trauma you say keep/kept you from learning to ride, whatever the cause of it was. (Perhaps you have long ago, but you didn't say in your post.) Once you have found someone to help you work through that, the other suggestions are good, to find a trusted friend or family member who will help you learn. If you can find a secluded place where you won't have to worry about feeling silly about other people possibly watching you, that would be ideal. (Little-frequented area of a park, parking lot behind a business not visible from the street, friend's back or fenced yard, secluded country road, etc.) Preferably somewhere without a lot of bumps, obstructions, and other hazards you may be afraid to run into or fall on.
Probably don't expect this to take only one day. Go in small doses-- 5-15 minutes of practice if that's all you're comfortable with. If uncertain, you might even stop before the point when you feel you "need" to and decide to start again another day; stop when you're still feeling okay about the riding rather than when you're starting to feel stressed out. Make sure the bike you're using fits-- being on something too large for you will be awkward and will not inspire confidence. You might feel more stable at first learning on something that isn't a road bike-- wider tires and heavier frame may feel more stable; wider handlebars and a more-upright position may help you feel more in control?
Wear a helmet. Hell, wear knee and elbow pads if it makes you less afraid of falling (as long as they're not a type that will restrict your movement). Make sure pant legs are rolled up and shoelaces are tucked away so you don't have to worry about your clothing or be afraid of it catching or being distracting.
And depending on how much anxiety you have around riding and just how little experience you have, I wonder if trying out an exercise bike for a while (to get used to pedaling, if that makes you nervous-- sometimes having to think about all the "things" about cycling at once-- balance, pedaling, braking, watching the road, etc.-- can seem to pile on), or if you know someone with a trike who will let you borrow it for a bit (getting used to pedaling and being out on the road, before you have to worry about balancing) might not help.