There are a number of ways one can gain an indulgence. There is a book published with most of the more common indulgences. I’ll give you an example of a couple of the most common ways.
Indulgences today are no longer classified in days, quarentines or years. There are only, “partial” and “plenary” Plenary Indulgences are pardon of all punishment due for sins, and partial are as the name sounds, some. The Most Common way to gain an indulgence is to offer prayers, lets say the rosary, you would do the following….
A Plenary Indulgence…
When the Rosary is prayed in
1. In a Church where the Blessed Sacrament is reserved, by a family group or
in a religious community.
2. Five (5) decades of the Rosary must be prayed continuously.
3. The prayers of the Rosary must be prayed vocally and one must meditate upon the Mysteries of the Rosary.
4. If the recitation of the Rosary is public, the Mysteries of the Rosary must be announced.
A Partial Indulgence…
One may gain a partial indulgence for the Rosary’s recitation in whole or in part in other circumstances.
A Plenary Indulgence… can be gained only once a day, except by those who are in danger of death. (In danger of death, there are no limits to the number of Pleanary Indulgences you may gain)
* to gain a plenary indulgence one must perform the indulgenced act with the intention of gaining the indulgence. You can make a resolution to gain all the indulgences that are availible to you and renew that inention, once a year or so, and that will suffice for any indulgenced act you participate in. Three other conditions must usually be fulfilled, In the case of the rosary the Lord’s Prayer, three Hail Mary’s and Gloria Patri, usually recited at the beginning or the end of the rosary (Depending on the custom you where taught) are for the intentions of the Pope. Normally you will see for an indulgenced prayer or charitable act, like feeding the poor, or reading the Bible for at least fifteen minutes a day. the words and the usual conditions, which means the actions below.
A sacramental confession
Prayers for the Pope’s intentions
So in order to gain an indulgence you must be free of mortal sin. If you are not in mortal sin, normally you would not need to go to confession. However it is advised you go to confession even if only you are only guilty of venial sins a you are more open to God’s graces.
So you can see, Indulgences are not that hard to gain, and don’t have to cost anything except your time, and loving devotion for God.
Here is a link, go forth and gain indulgences……