Verb conjugation tables will show you the conjugation rules for imperative (command) mood in Italian.
All imperatives follow the same rules of changing a positive command to a negative command by simply adding "non" to the imperative form, with ONE NOTED EXCEPTION:
Although the second person singular (the "tu" form), uses the appropriately conjugated form of the imperative for positive commands, it ALWAYS uses the INFINITIVE for NEGATIVE COMMANDS. And, of course, the "tu" form is VERY common. We usually tell someone familiar to us to do or not do something.
Vieni qui. (You) Come here!
Non venire qui. (You) Don't come here!
Venite qui. (You all) Come here!
Non venite qui. (You all) Don't come here.
Pensa più. (You) Think more!
Non pensare troppo. (You) Don't think too much!
Pensate più. (You all) Think more!
Non pensate troppo. (You all) Don't think too much!
Buried deep in the verbiage on the website:
"To make a negative command (don’t do something), simply put non before the imperative. Tu is the exception. Here use non + infinitive."
https://www.thoughtco.com/the-imperative-mood-in-italian-4072739 is also a very good site for more explanation.