To add error bars in Excel:
Click your chart to select it.
Select Chart Design- Add Chart element-Error Bars.
Select the Standard Error, Percentage or More Options as custom values.
In More Options, fill in Custom and enter in your values or a range of standard deviation.
Adjust when necessary...
On a Chromebook, it is very easy to cut and paste:
To cut Ctrl + X.
To copy: Highlighting and pressing Ctrl + C.
To paste: Click to the desired place and press Ctrl + V.
You get the option to right-Click and cut, copy or paste too.