You're trying to edit an array formula, and you're stopped in your tracks. You click the formula in the cell or formula bar and you can't change a thing. Array formulas are a special case, so do one of the following:
If you've entered a single-cell array formula, select the cell, press F2, make your changes, and then press Ctrl+Shift+Enter..
If you've entered a multi-cell array formula, select all the cells that contain it, press F2, and follow these rules:
You can't move the individual cells that contain your formula, but you can move all of them as a group, and the cell references in the formula will change with them. To move them, select all the cells, press Ctrl+X, select the new location and press Ctrl+V.
You can't add new cells to a block of result cells, but you can add new data to your worksheet and then expand your formula.
After you make your changes, press Ctrl+Shift+Enter.
Finally, you may be able to save time if you use array constants—parts of an array formula that you type in the formula bar. But, they also have a few editing and usage rules. For more about them, see Use array constants in array formulas.