Select the cell where you want the average to appear
Type `=AVERAGE(range)`
Replace `range` with the cells you want to average, such as `A1:A10`
Press Enter
To average non-adjacent cells, use `=AVERAGE(A1,A3,A5)`
To average an entire row or column, use `=AVERAGE(A:A)` or `=AVERAGE(1:1)`
To use the AutoSum menu, select the cell, click the arrow next to AutoSum, and choose Average
To average visible cells only, use `=SUBTOTAL(1,range)`