Unable to create directory

First issue is related with ownership of the directory.
Second issue is, you will have to make directory within directory so consider using following UNIX command:

sudo mkdir -p wp-content/uploads/2014/08

here p flag lets you create directory within directory
Third issue is related with the file permissions ( theme-editor.php)
use :

ls -lah 

to view the ownership and permissions of the file.
or consider following code to change the permission of file

sudo chmod 755 theme-editor.php

and then try to do whatever you want to do with files.
I hope it helps.