you are only jacking up the front enough to take the weight off the front suspension, otherwise when you loosen the pinch bolts it can slide uncontrolled all the way down.
It maybe easier to put the bike on its centerstand and put some weight towards the back, or have a mate sit on the back of the seat to raise the front. you just need some daylight under the front wheel.
Here are the 4 pinch bolts you are going to loosen, once you have the bolts loose you may need to GENTLY spread the yokes open with a flatblade screwdriver or such.
Now that said, sliding the fork tubes up in the yoke also lowers the front end, reduces your suspension travel, and changes the geometry, you can go too much and the steering become unstable! Tank slappers are no fun. You should also go exactly the same on both tube, not eyeball, or ruler close, but within a couple .001" on a set of vernier calipers / Mics
Clip-ons were designed go under the top yoke and you not have to slide the tubes. They make different height... but that will mean not using the factory headlight ears, the make aftermarket ones that are from $15 on up depending on how nice you want.
If you do slide them you may want to lower the rear as well to keep the changes less than an inch difference between front and back. Although I LOVE the looks of this CB750, "Anvil", here is an example of too much. There is virtually no suspension travel left because the fork tube are slid way too far. It may look Cool and mayeven be ridden, but not in the real word where I live, pot holes, railroad tracks, even speed bumps would bottom it out and I GAR-un-TEE the rake / trail / catsor numbers are crazy unstable.
81 Honda CB750C - Current Project
67 BSA Spitfire MkIII - Next Up (Full Resto)
81 Honda GL1100 - Bob / CafeĀ“
80 Suzuki GS750L - Bratstyle
72 Honda CB450K5 - Basket Case
73 Honda CB350F Cafe' (Gone but not forgotten)
Don't wait for opportunity to knock... kick the door down and drag the old harlot in!