So you want to know how to inject Ritalin? Well, if you're talking about Ritalin capsules - then here's an idea:
DON'T DO IT!
Book yourself into some sort of drug counselling session instead.
I'm not trying to dampen your party lifestyle, but most pills and capsules (including Ritalin) contain a significant amount of fillers and binders.
If you try to "cook up" and inject Ritalin capsules, you will also be injecting these fillers (usually stuff like talcum powder) into your veins or muscle tissue.
Why is that a bad thing?
It can cause all sorts of nasty medical complications, and can prove fatal in certain circumstances.
Don't believe me? Book that drug's counselling session then. Even if they don't manage to convince you to give going clean a shot, they might at least advise you on how to stay safe and how to avoid injecting harmful chemicals into your body.