How does a Knife Edge work? Without using the wings for lift, what gives the plane its lift? Thanks in advance...

The easy answer is the fuselage gives the lift. The involved answer includes power settings, vertical stab and rudder and the canopy. On a biplane the interplane struts, out near the end of the wings, helps allot and gives the rudder much more authority.

Take the H9 Showtime with the Side Force Generators (SFG) as an example. Fly it without them installed and you need a a few degrees of rudder to hold a "normal" nearly level knife edge. Install the SFG's and now you need very little rudder to do the same knife edge.

Take a look at an airplane fuselage. Look at it from the top. Big and fat in the front with a large radius. Tapered back to a point in the rear. It's an airfoil. Not a very long airfoil--but it's an airfoil.

The whole plane is an airfoil. Look at the prop. Rotating airfoil.

How it flies or at what attitude it flies just depends on how you orient it.

With the wings vertical in reference to the ground, there is no vertical lift except for the fuselage.(lift is always perpendicular to air flow over the wings). The shape of a fuse does not provide as much lift as a wing but if designed for knife edge flight, it will be enough to hold steady and even maneuverable enough to turn,climb and go up or down.Its also best to have a fully symetrical airfoil for knife edge flight,this type of airfoil can have 0 lift at zero angle of attack, which requires less control inputs to maintain headings.
With that in mind,look at some of the best knife edgers-pattern planes,H9 Showtime,Hyde Vision,Ultimate Bipe-all have the fuse and SFG's to make knife edge easier.(there is more side area up front to make the in-flight CG forward and more controlable).To take it to an extreme, the U-Can_Do has a tall fuse up front with the canopy way up there and a very narrow fuse too,it can hold knife edge at slower speeds than most other planes.
When first starting to fly in KE, get the plane up to safe height,roll 1/4 roll until top of plane is facing you and keep it in that attitude to observe what happens(full throttle at first). Most will start dropping some, to maintain a steady altitude, rudder must be used since its now horizontal like the stab usually is when upright.Once the right amount of rudder travel is achieved, the plane will hold level flight and then you can start adding other controls to turn or keep the plane from rolling if needed.Start out by just flying straight lines at first, then later you can try turning/climbing in KE or 4 point rolls.