Exactly the same as a normal Diabolo Throw except that your arms are crossed over, you will not be able to throw the diabolo nearly as high with your arms crossed but this is a useful 'exit move' to get out of tricks that leave you tied up. Or tricks that have simply gone wrong!
Spin the diabolo then perform an Unwrap & recapture to end up with your arms crossed over. Hold the arm on top as flat across your chest as you can manage & extend the arm to hold the tip of the handstick as far to the outside of your body as possible. Keep the hand on the bottom pointing straight out in front of you so that the diabolo is hanging just to the side of you. Make the throw using the arm on the bottom only, keep the arm on top as still as you can. Quickly push the arm on the bottom out to the side, try to keep the sticks at the same height as much as you can for a vertical throw.
If you want to toss the diabolo out to the side (useful for leading into some other move such as some Circular Throws or an Sun between the arms) you can pull the bottom handstick diagonally downwards.
More often than not you will uncross your arms while the diabolo is in the air & catch it normally. If you want to you can catch it with your arms still crossed over (or uncrossed & recrossed the other way) just remember to keep the string pulled tight & line up the tip of one handstick with the axle.
Another option is to catch the diabolo by circling the handstick held by the arm on top over the top from the inside to the outside then back underneath the axle, just like the recapture part of the Unwrap & recapture move. Pull the arm on the bottom outwards as you move the other handstick over the top of the diabolo & pull the string tight. This puts you back at the beginning with the diabolo spinning in front of you with your arms crossed over the opposite way round to that which you started with. You can then make another crossed arm throw back again & keep going from side to side in this way.