So you use the infinitive to give an order? Does it only work in the negative, or would you also say "Venire qui" for "Come here"? If it's true that you use the infinitive for the imperative, then this is WAY easier than French, but I have a feeling that there is more to it. :)
There is more to it, but fortunately negative commands are just that simple :) you're usually safe with the infinitive, but you can also use the second person plural to address multiple people. Non venite qui would be just fine.
Moving away from negatives... the imperative has a separate conjugation for -are verbs, such as parlare, mangiare, cantare. (Note that the second person conjugation looks like the third person present indicative)
- Speak louder! Parla più forte! Parlate più forte!
- Eat something! Mangia qualcosa! Mangiate qualcosa!
- Sing a song! Canta una canzone! Cantate una canzone!
The other verbs, ending in -ere and -ire, generally look just like the present indicative, with some exceptions you'll learn as you go along, such as sapere: know that I love you! Sappi che ti amo!