He sealed off the Jubi into his body and make use of the 10 tailed beast’s chakra.

He knew that the Jubi’s chakra was too great that it would break until the Jubi would be released and wreak havoc to the land. So, when he was dying, he divided the Jubi’s chakra into the 9 tailed beasts and disperse them into the land and then sealed its empty body and sent it off the sky which became the moon.

Based on the Naruto Manga chapter 467 page 12 as told by the Uchiha Madara, these secrets of the Rikudo Kage were carved in the tablets that has been passed through the Uchiha clan for generation. These tablets until now lie beneath Konoha in the Uchiha Clan’s secret meeting place. Those with the eyes power are those who can read them. Each eyes power level can read something from Sharingan, Mangekyu Sharingan to Rinnegan.

So since Uchiha Madara got all these level (Pain who was once with Uchiha Madara was a Rinnegan user), he knew all the info written on the tablets.

Jubi is actually the fusion of the the 9 tailed beasts that possess the strongest chakra. The chakra was great the it would break once the Rikudo Sage died and would once again wreak in havoc to the land.

When the Rikudo Sage was dying, he used his remaining chakra to divide the Jubi’s chakra and disperse them through out the land. That’s how the 9 tailed beasts started to exist.

The 9 tailed beasts are actually just the division of Jubi’s chakra.

And after that, the Jubi’s empty body was sealed away and sent it to the sky where no one could reach it and it became the moon.