well I just finished making my BC wheel, and holy crap its hard to ride, i can make it about 3 feet then i fall down hard, can you give me some pointers please, I havn’t felt this helpless since i started riding uni.
how I learned is to hang onto a tree overhead then swing myself slightly. you can get momentum, then you’ll kind of figure out how it works. after you get like five feet, you’ll be good, and can start going farther.
BC wheel hints
Being too intelligent to actually attempt it myself, I have nonetheless noticed a few things while watching three of my kids learn it.
They found a little gentle hill to learn on (dirt). Then, they drove two metal fence-posts into the ground about 3 feet apart. They used these to balance themselves while mounting the wheel, and to give themselves a little push with. A couple hundred tries later and they were all doing great, having each broken the hundred foot barrier and earning the promised twenty dollar bill. 
i found two poles in the corner of the gym i practice in and pushed/pulled myself to going forward and got 20-ish feet that way. once i had that i started trying the rolling jump mount which i think is easier to keep going/get going with. it’s somehwat harder to get on the thing that way though.
As other people said, get two objects and push off between them (like two lawn chairs). That’s how I learned.
This method allows you to get the hang of the riding half of the BC wheel before you try to attempt mounting. After you get a good idea of how to correct balance and such, then you can procede to learning the jump mount or skate-mount.