How did stalin break the agreements of the yalta conference?

  Stalin did not conduct free elections in Eastern European countries

Explanation:  The Yalta conference was held in February 1945, during which the leaders of America, Great Britain and the USSR decided, among others,  on plans to be implemented after the war. According to these plans, Stalin was supposed to conduct free elections in Eastern Europe. He did not do that and he broke the deal. Namely, Stalin imposed communism in the Eastern European countries, under the pretext that free elections were held and in fact it was not so. In all countries he sent his emissaries, who directly influenced the outcome of the election, despite the election results.