Now for the important part. How do you change the permissions of a file. That is where the chmod comes in.
First, you have to actually have permission to change permission of a file. That means the file has to belong to you. So if you are user maryjane and you want to change the permissions of a file belonging to jlwallen, you will be out of luck (unless you know the password for either jlwallen or the root user). But if you are the owner of the file you can change the permission.
Say you want to create a bash script (we'll call it script to do something and you have to make it executable. To do this, add the executable permission chmod u+x script. That will add only the executable permission to the file.
If you want to add write permission you would issue the command chmod u+w script.
To grant read permisison you would issue the command chmod u+r script.
In order to give all three permissions use the command chmod u+rwx script. You can also remove permissions the same way - only you exchange ~ezentity_quot+ezentity_quot~ with "-".