A certificate of receipt of your application ("Attestation de réception du formulaire de demande d'attestation OFII") will be sent to you by mail. This provisional document will attest to the legality of your stay in France until the validation of your visa by the OFII. In concrete terms, if you have received a long-stay visa from the consular authorities, you must contact them within three months of your arrival in France to have the visa validated. The OFII is located throughout France thanks to its network of "territorial offices".