You can login to your user panel and go to the file manager and travers to folder in question and set the permissions from there.
Note that you will need to check the owner of the files. If they are owned by 'Apache' you will need to change ownership first so that they are owned by your user id. This can be done via ssh (shell). If you do not have ssh (shell) access, contact your host and ask them to chown the files to your user id. If this is not done, you will not be able to change permissions and you may have problems getting the scritps in Joolma to run.
We currently have users running Joolma and we had to do this for them as well since we do not give out shell access on our servers.