I have a folder and i can't paste anything or save anything in it. Can i change permissions in terminal?

Yes. What directory are you trying to put the data in? Paste the output of:

ls -ald /path/to/dir
ls -ald /path/to
ls -ald /path
ls -ald /

Also what user are you logged in as? You can find out by typing id .

You can grant everyone read/write access to the directory but that is usually a bad idea.

I am only user i installed ubuntu 9.10 yesterday and can you give me the code to grant everyone read/write access.

* This is dangerous from a security standpoint

chmod -R a+rwx /path/to/dir

login as root
then use the following command
chmod 777 filename to make it read,write and execute

sudo chmod 777 FILENAME

NOTE: This is really NOT recommended for all the files. Be extremely careful while using this.
alternatively you can do chmod 644 which will only give write permission to the root user and everyone else gest only read permission.