Remove the rear wheel & forks. Put a garde 8 bolt through through the rear axle holes, (use spacers to make sure the chain stays centered between the axle holes). Attache the other end of the chain to a tree or other ridgid object. Loop a heavy duty tow strap around the steering head attach a winch or come-a-long to the strap and another ridgid object. Now start pulling SLOWLY. You'll be amazed at how the frame pulls back to its correct shape. If you don't go slow it'll go too far before you can stop it.
The forks will be more difficult. Put them back on, remove the wheel and put a grade 8 bolt through as in the rear. Attach the tow strap and start pulling VERY, VERY, VERY SLOWLY. Monitor your prrogress carefully. Too fast and the frame will try to deform again, or the forks will bend out. Hopefully, the steering head will return to it's correct rake.
This is only a start but it might get you in the ball park.
Caution! Don't let anyone near this while you're pulling. Winching of any kind is VERY dangerous. The come-a-long puts you directly in the line of fire if something breaks, so take measures to protect yourself. Each time you stop to check your progress, walk up to the frame from the sides, not the front or back, and don't get too close.
Once you get it where you want it, check all welds & repair. Especially the steering head, (it looks pretty bad).
Good Luck & work SAFE.