To turn a positive sentence into a negative one, simply insert "не" before the verb, unless that verb is "има". (The verb "има" has its own negative counterpart that you encountered in the A-verbs (part 3) tutorial.)
When negating verbs other than "има", sometimes "не" will be directly in front of the verb, other times it will be separated from the verb by other short words, such as the short form(s) of the reduplicated pronoun, the clitic "ќе", etc. Since we have not yet studied the reduplicated pronouns or tenses other than the present, negation for now is as simple as inserting "не" before the verb.
However, note that with verbs such as "се вика", the "не" will precede the entire verb: "не се вика".