Follow these steps:

Press Ctrl+H to bring up the Find/Replace Dialog.
Choose the Regular expression option near the bottom of the dialog.
To add a word, such as test, at the beginning of each line:

Type ```^``` in the Find what textbox
Type test in the Replace with textbox
Place cursor in the first line of the file to ensure all lines are affected
Click Replace All button
To add a word, such as test, at the end of each line:

Type ```$``` in the Find what textbox
Type test in the Replace with textbox
Place cursor in the first line of the file to ensure all lines are affected
Click Replace All button