How could I put them on?
You'd have to modify where the axle goes by drilling it out. I think there's a bit more to it than it being as simple as that though. The Cafe Race as-is uses one of the typical set screw axles(common in many yoyos). This was done to keep costs low. The same tactic was used on the Burnside, for example.
So, like has been said twice: as is, no way. You need the appropriate skills and tools and knowledge to make the modification to make the Cafe Racer compatible with Side Effects.