The customary indulgence associated with the celebration of All Souls’, November 2, has been extended for the full month of November. See the article at the link for more details: Vatican News: Plenary Indulgence
How to obtain a plenary indulgence:
Visit a Church or Oratory. A plenary indulgence, applicable ONLY to the souls in purgatory, may be obtained by those who, on All Souls Day, piously visit a church, public oratory, or -for those entitled to use it, a semi public oratory. On visiting the church or oratory it is required that one Our Father and the Creed be recited. This can now be done spiritually. So, offer these wherever you are on November 2.
Visit to a Cemetery. Only applicable to the souls in Purgatory when one devoutly visits and prays for the departed. Usually, this applies to the Octave (November 1 to 8) only, but is now extended to the whole month. The visit to a cemetery may also be spiritual in nature. See the article linked for details on this exemption.
One must also pray for the Holy Father’s intentions, worthily receive Holy Communion and go to Confession within the month (ordinarily within 20 days of All Souls). To gain a plenary indulgence one must be free from attachment to all sin, even venial. Otherwise you will gain a partial indulgence.