Please give me any help, thank you in advance.
I would remove the larger of the two leaders because the smaller one will be a little easier to graft to. But either will work.
Here’s a suggestion: cut off the smaller leader about 8-12 inches above the fork and do a simple cleft or wedge graft. If your scions are small do two scions in one cleft, and if they are large do one scion in a wedge. After they are well established cut off the other, larger leader at about the same height, and go ahead and do two grafts in one cleft. Once you have a clear winner remove the leader that lost the race and eventually eliminate all but one scion -probably next year. Be sure to provide protection for the young grafts -a stick lashed to the trunk for birds to perch on, hardware cloth wrap around the bottom 18" or so of tree to discourage rodents, and a fence of some kind to keep deer from browsing on it. I use the relatively cheap welded wire fencing, at least 4’ high and 30" diameter, so a 9’ or 10’ length of fence rolled back on itself. Remove competing grass until the tree is well established. A nice long stake driven into the ground next to the tree is handy if you need to pull it straight. Keep the tree from drying out. And water it well a couple of days before grafting.
If you prefer you could do one leader this year and then decide whether to remove the other next year, just for insurance.
Some people prefer bark grafts in such situations, but I have problems with those on larger root stocks- not everybody does. And if the wood is slipping nicely you could even do a bud graft on the smaller leader. But buds (and chips, for that matter) are attached to the side of the root stock compared to clefts, wedges, whip, or whip and tongues being “in line”, which makes a nice looking tree. But they all work.
If you can, locate some freshly pruned water sprouts or such and sit down with your tools and practice with those. Good luck and have fun!
My somewhat different suggestion… Leave both, use the bigger one, cut it off where it is marked (it is better looking of the two); you can use several grafting methods - bark, cleft, whip and tongue, side grafting…, but I suggest bark or cleft grafting with the addition of 1-2 more grafts lower on the tree using the side grafting method, for insurance and practice; bark grafting is the easiest and I see no problem using it on this rootstock. You can use one or two scions - for the cleft method two, for the bark method one or two. If both/all scions take, when it heals over, remove all but one. If you choose the bark grafting method, I suggest finding a somewhat flatter part on the cut (the flat part of the circle) for better contact, but it’s not mandatory. When bark grafting, the bark has to be slipping. Also, on the other leader, you can practice grafting without cutting it off - using side grafting or budding (chip) + the other actions that marknmt suggested (protection)
