If you want to write date in the selected area you can use write cell and specify, cell values, if you want to write data next to the existing table use append range, to read the data just give read range with out mentioning the range in read range activity.
in append rang you cant specify column name from which you want to append it ways takes by default columns as column A, whichever cell is free in column A data will start appending from that cell.
then last option is use read range get the index of last row, (lastrow+1 or last row+2) will be your cell number and now use write cell start with lastrow index the increment one inside loop .
How can I use read range to get the index of the last cell used?
you can get the count of rows check the difference between count and your speadsheet last column (you might add 1 or 2 based on header and the index)
how can I say to write range that is the place I want to put the data?
check the new data tab;e is same as your existing one if yes then mention A"yourlast index+" value in write range activity