This is based on several Kubota loaders of this vintage I've seen - but I don't have a 650. (Cheerful refund if something isn't right)
The two bars stored up above the dash are the lower supports. The end with holes goes at the bucket just above the lower pin, use the loader's front retainer bolts to attach them. The other end of the lower support has a flat foot - works best on a hard surface. Curl the bucket forward until these are in place.
The other 2 bars (under the platform) mount vertically and hook to the lower supports about midway. The upper end fits over a pin on the loader arms. (Raise the bucket until you can get the pin into the slot - put in the hat pins to hold them.
With the support bars in place, and on level hard ground, you can take out the post retainers and, using the loader control valve, lift the posts off their perches (same motion as curling bucket back). Lift the posts just enough to clear - don't stretch the hoses. Then lift the front of the loader frame (same valve motion as lowering the arms) Shut off the engine. You should now be able to take apart the hydraulic couplers. Plug the supply line back into the return line so the hydraulic system will work with the loader removed.
In the photo of your brother's tractor, it looks like there's a white sticker on the right loader post - Kubota sometimes has a diagram there showing the loader removal.
It is important not to let anybody near any part of this while you're moving things hydraulically. Safety is a big issue, best to go slow until all aspects are clear to you.
After you've done it a few times it'll be easy.
Hope this helps.
Dick Bargeron