You are here in the PRoC BLE forum, but you should be in PSoC5 forum. Probably not all helpers may read your question.
The I2C source code is nothing you normally have to deal with, what you need to use are the APIs which are documented in the component's datasheet which is always a mouse click away. To access a second slave you just have to know its address. When sending an I2C_MasterSendStart(you) have to provide that address as the first parameter. Anything else will be handled by the generated software. This is how to deal with multiple slaves.