To create a formula in Microsoft Excel, you can do the following:

1. Select the cell where you want to enter the formula
2. Type the equal sign (=)
3. Type or select a cell, or type in a function, like SUM
4. Enter an operator, like minus (-)
5. Select the cells or range that are part of the function
6. Press Enter (Windows) or Return (Mac) for the result

You can also use AutoSum to quickly sum a column or row of numbers. To do this, you can:

1. Select a cell next to the numbers you want to sum
2. Select AutoSum on the Home tab
3. Press Enter (Windows) or Return (Mac) 

Once you create a formula, you can copy it to other cells. To do this, you can:

1. Select the cell with the formula and the adjacent cells you want to fill
2. Click Home > Fill, and choose either Down, Right, Up, or Left
3. You can also press Ctrl+D to fill the formula down in a column, or Ctrl+R to fill the formula to the right in a row