How wonderful you have discovered this wonderful devotion. I would highly recommend you read her diary. It is a big book but only costs about $15. There are several smaller books on the divine mercy and devotions in this area: “Will You Help Me? - Handbook of Devotion to Divine Mercy,” “Jesus I Trust in You,” and The Divine Mercy Message and Devotion." “Will You Help Me?” is my favorite but they are all good and each has stuff that the others don’t have. All are available in Catholic bookstores or by mail order or over the net.
Jesus wants us to pray for mercy, not only for ourselves but for the whole world. Another prayer is “Jesus, I trust in You.” this is what is written at the bottom of the divine mercy image. This mercy devotion is part of my charism so am delihgted to offer info to anyone interested. The Lord gave me specific instructions, like Faustina, that I am to pray in this area. Another good thing is to get a cassette or CD and you can then pray the chaplet anytime, even when driving. It is also broadcast daily on EWTN. Adn it is easy to memorize and you use regular rosary beads. But keep in mind, so that you and others of you that read this reply, the prayer “Eternal Father, I offer You the Body and Blood, Soul and Divinity of Your dearly beloved Son, our Lord Jesus Christ in atonement for our sins and those of the whole world” followed by “For the sake of His sorrowful passion, have mercy on us and on the whole world.” this is the important prayer. It does not have to be prayer any specific number of times. St. Faustina was to pray this repeatedly and she didn’t keep count. Just pray these mercy prayers. Don’t worry about the order or the number of times or even about saying all of it. Just pray for mercy. Don’t get caught up in the details. Praying for mercy is the all-important thing. At the end of the formal chaplet the prayer that is said three times: “Holy God Holy Mighty One Holy Immortal One, have mercy on us and on the whole world.” can also be said by itself. Adn if you "memorize the chaplet ot music, which is what will be done on a cassette or CD or the TV program, you can just sing it off and on throughout the day. Next to the Hail Mary adn the rosary this chaplet is the most beautiful prayer there is.
Pray for mercy! It is Jesus’ request and order!