I do admire your intention to learn to ride. I really do.
Had you thought of riding around Orlando looking for a horse riding centre? I hear there are lots.
Go in, get talking with folks wearing riding breeches.
Tell them that you have got access to a nice gentle horse
And then ask them very kindly, if they can come round to your place and help you tack the horse up.
Explain that you are a complete novice but that you love horses and you want to have a go. "You need, repeat need (practice how you can say it appealingly) help".
You never know, someone might take pity on you and if you are half as convivial in person as you are on this forum, then you might get lucky.
PS That long suffering horse of yours is a candidate for pulling an angel's chariot.
PPS If you are practising bareback riding, then you need either a thick rubber straight bar bit or a bosal (rope based hackamore). Neither will hurt the horse's mouth.