suppose price of a good is higher than the equilibrium price .explain the change that will establish equilibrium price ?

In case the market price is higher than the equilibrium price, then there will exist excess supply in the market. To put in different words, there will be a higher supply in the market as against the demand. This will increase the competition among the sellers as each will compete with other to sell more of his output. To induce the customers the sellers will start reducing the prices and consequently, the market price will fall. This fall will continue until the market demand equals market supply. In other words, the market price will fall until the equilibrium price is reached.

To have a clearer understanding of this topic you can also refer to our study material. You can find this topic in Microeconomics- Market Equilibrium (Lesson 1) of our study material.