Thomas Putnam is a wealthy man in the town, who is greedy, and feels like land that he deserved had been taken away from him in his father's unfair will. He fights with Proctor and Nurse over land boundaries in Act One, revealing to the audience just how land-hungry he actually is.
Another important fact is that his daugher, Ruth Putnam, is one of the girls that are making a whole lot of accusations against people. One other fact: if you are accused of being a witch, and plead guilty or not guilty, your land is turned over to the city, and anyone who has the money can go and buy it.
So, enter the scheming and land-hungry Thomas Putnam. George Jacobs has land next to his, quite a bit of it. If Jacobs is accused of being a witch, Thomas, who is quite rich, can buy up his forfeited land. This will increase Thomas's acreage by quite a bit. So, he "nudges" Ruth to accuse George Jacobs of witchcraft. He hints things at her, suggests his name as a possible culprit, and gullible Ruth follows through. And what's even more, there was a witness that heard Thomas Putnam say that in accusing Jacobs of witchcraft, "his daughter had given him a fair piece of land." So, it was confirmed that Thomas was indeed, murdering people in order to get ther land.
I hope that clears things up for you a bit; good luck!