1 By mouse:
When you want to copy & paste between edit boxes of window program, take your mouse first, and place your cursor at the beginning of the text in the box as below, then click and hold the left mouse button, while pulling your mouse over the text. This will highlight the text. After that release the left mouse button. Now, with the cursor over the highlighted text, right click the mouse for options, and select 'copy'. Now over the another empty box as below, right click your mouse again, and select 'paste' and you will have copied and pasted the text.

Cut and paste is the same as above, except you choose 'cut', instead of 'copy'. After you select cut, the original highlighted text will be deleted.
 

2 by Shortcuts  of keyboard
To Highlight: Press 'Ctrl' + 'A' or "Shift" + Arrow keys.
To Copy: Highlight an area, as shown above, then hold 'Ctrl' + 'C' (For Mac users 'Apple' + 'C').
To Paste: Click your mouse where you want the text pasted, and then press 'Ctrl' + 'V' (For Mac users 'Apple' + 'S'.

The ability to cut, copy, and paste is found in most programs. Sometimes, the ability to do these tasks via the mouse is disabled, but is still quickly achieved through the use of the key shortcuts outlined above.