Hi @hoa_le​ - When adding the Excel Reader to your FME workspace, click on the and the Parameter button. In the following Excel Parameters window, you'll have options to specify which row you'd like to read from:

For writing to a specific row in your Google Sheet, after adding the Google Sheet Writer to your workspace, open up the Writer Feature Type Parameters. You'll find parameters that will allow you to control where in your sheet you'd like to start writing:

I hope this helps!