This is a regular verb. It follows the conjugation pattern of the verb falar.
This verb is common in informal Brazilian Portuguese. It is rare or unfamiliar in European Portuguese, where expressions like 'integrar-se' or 'fazer parte do grupo' are more natural.
Infinitive:
Ela está tentando se enturmar com os novos colegas.
She is trying to fit in with her new classmates.
Preterite:
Na primeira semana, eu não me enturmei.
In the first week, I didn't fit in.
Present Subjunctive:
Espero que vocês se enturmem rápido.
I hope you all fit in quickly.