If you’re interested in tweaking your WordPress site to suit your needs, chances are that at some time or another you will need to edit some of the theme files, if you want to get exactly what you want.
Fortunately, WordPress makes this very easy by providing an in-browser editor that you can access from within your WordPress admin area. Without that, you would need to use FTP and edit the files directly.
Getting to the editor
Once you have logged in to your admin area, select the Appearance menu from the sidebar on the left-hand side of the screen. From there, you will see the Editor menu (this should not be confused with the Plugin Editor, which can be found under the Plugins menu and enables you to edit a different set of files).
Editing the files
You’ll now be presented with a screen like the one to the right. From the right, you will see all the theme files for your currently active theme. (You can edit files of other themes by selecting the theme from the drop-down in the top right hand corner.)
On the right is a listing of all the files – the most common of these are header.php, single.php, page.php, footer.php and index.php. It depends on what you are trying to achieve as to which file you will want to edit. The tutorial should explain which file to edit.
Limitations and notes
Note that in order to edit files from within the editor, the files themselves will need to have permissions of at least 666. The built-in editor also has some limitations, which other editors don’t have. For example, there is no search/replace function, no line numbers, and no highlighting.