First download Paint.net. Save the YouTube logo on your computer and then open it using Paint.net. Press S and select the "You" from YouTube, once selected press delete. Now press F and choose the white color, pain the deleted area to fill it with the white color. Press T to select the text tool, select the font Arial Narrow and choose the font size 144, press ctrl+shift+N to create a new layer. Now click on where you want to the text appears and type anything you want. Go to File and Save As, save the file and make sure the file type is JPEG. When you have saved it will ask if you want to flatten, select Yes.