Ich stelle mich vor.
English: I introduce myself.
In German, some verbs are reflexive. 'Sich vorstellen' is a reflexive verb. It can mean to introduce yourself or to imagine something, depending on the context. At the beginner level, you usually use it to say your name and introduce yourself.
Use 'sich vorstellen' when you want to introduce yourself or someone else in German. For example, when meeting new people, you say your name using this verb.
Ich stelle mich vor.
English: I introduce myself.
Wie stellst du dich vor?
English: How do you introduce yourself?
Wir stellen uns vor.
English: We introduce ourselves.
Er stellt sich vor.
English: He introduces himself.