Dig it up, put it in a large pot containing a soil-less mix (like Miracle Grow potting soil or whatever--NOT garden soil, which isn't meant for containers). Bring it inside before the weather turns cold because mangos cannot tolerate cold weather. Keep it in a warm room and in a sunny window in order to overwinter it indoors. Don't water it too much in winter because it won't have a lot of active growth going on. Mangos are tropical and cannot survive sub-freezing temperatures or frosty weather, especially when they are young. If your tree were 5 or 6 years old, it might be able to handle a couple of hours of temperatures down around freezing, but young ones have less cold tolerance than even that. I think that they have to be grown in zone 9 or higher (10, 11, etc.) in order to survive in the ground. Oklahoma is zones 6 (more northern parts of the state) and zone 7. If you happen to have a heated greenhouse or a sunroom, either would be ideal for a mango. Eventually you'll have to let it go because eventually it will get too big to carry indoors in winter.

as far as I know, you need to move to south Florida with your tree... ;)

Moni

i really appreciate yall, ya i know i picked a great fruit tree to grow in oklahoma lol. i was tryin to decide if i should keep it indoors or just buy a greenhouse like a cold frame or somthin an just keep it heated. im from mooreland an fruit seems to do really well here. This is gonna be my challenge to keep this tree alive for as long as i can. maybe cause its so small ill just keep it inside for this winter with soil-less mix like you said an start workin on a greenhouse for next year.

an yes i think movin to florida with my tree would prob. be the best thing lol, i know my wife wouldnt complain bout it