You could refer to code example CE220818 I2C Master High Level (Navigate to PSoC creator-> Code example)
Cy_SCB_I2C_MasterWrite() is used in this code example.
The MasterWrite function is a high level function that takes care of sending the start and the address for you. No need to proceed with a SendStart.
SendStart is a low level function. Generally those two should not be mixed.
The PDL documentation has a in depth description of the different use cases, if you just click on the I2C tab in the PDL document it describes how the different API are used.
Here is where the PDL lives on my machine.