The "necesitas" tells us that it's the familiar you (tú) form. For the first person singular form (I), it would be "necesito". In the present tense, the endings are distinct.
I'm giving a condensed form here that mostly avoids differences in -ar, -er, and -ir verbs: First person singular (I) always ends in "o", first person plural (we) always ends in "mos", second person familiar singular (tú) always ends in "s", third person singular (él, ella, usted) ends in "a" for -ar verbs and "e" for -er and -ir verbs, and third person plural (ellos, ellas, ustedes) always ends in "n".
Here's a more complete set for regular verbs of all three types: https://www.wikihow.com/Sample/Present-Tense-Conjugation-of-Regular-Spanish-Verbs