can I upload and use NextGEN Gallery via FTP only

Hello,
I am new to WordPress and I am running a website that uses NextGEN Gallery.
While trying to add a gallery, i got the following message:

“Directory wp-content/gallery/ is not writeable !
Check this link, if you didn’t know how to set the permission : http://codex.wordpress.org/Changing_File_Permissions“

I understand I have a file permission problem, but the link is a bit to advance for me, and unfortunately I dont have the time to study what things like ‘suexec’ mean 🙂

Via FileZilla I uploaded a new folder into wp-content/gallery/ called ‘test’ and i was wondering why i still cant see it on the plugin page in wordpress?
if it makes any difference, the guy who set up the site put the permissions of the folder wp-content/gallery/ to 755.
I really don’t want to cause damage and so i wonder if i can do it somehow without changing permissions.

Thanks!