Search And Replace Text in VI editor

ok, on the example text file above, lets say i want to change all the 'wallpaper' to 'screensaver' well this is how you would do it.. 

lets assume that wallpaperama.txt is located on my home directory at: /home/me/wallpaperama.txt 

step 1. open the file with the vi editor:

step 2. Enter – SHIFT + : (the Shift key and the colon key at the same time) on your keyboard, the screen will look like this: 
 

step 3. now enter this command and hit enter

step 4. now you will see that all the text 'wallpaper' was changed to 'screensaver' 
 

step 5. save the change with this command:

DONE 

i hope this helps you