Unfortunately i can not access your link. So i can not see any command you used. Don't confuse with permission. There are two things, permission and owner. Sometimes permission auto change when we copy some folder or file from pendrive or somewhere. That is because, when your system found any harmful or not recognized executable file it changes the permission immediately so the file failed to run. It's fully security issue. But sometimes Beginner user face this problem and get bored with it.
If your folder permission change then right click on it, you will see this..
You can see three group, "Owner , Group, Other". Just change the permission as you need. Sometimes you will see like this..
Something different here !! Owner is root not you. So you can not change permission from here.
You can change permission using terminal also
chmod 775 /media/folder/folder
three number : owner permission=7, group permission=5, other permission=5
write permission=4, read permission=2, execute permission=1
It only work if you are the owner of the file or folder. But what happen if you are not the owner? Don't worry, take the root's power, use "sudo"
sudo chmod 775 /media/folder/folder
And last one, how to change ownership
sudo chown your_usrname:your_username /media/folder/folder