ls -a will show you the permissions on the file, to the far left. They are grouped in three lots, the far left three are permissions set for the owner, the next three are permissions for the group and the last three are permissions for the world. There are three main flags on these permissions:
r = Read
w = write
x = execute
If one of these flags is present in whatever grouping it means that that person/group of people can conduct that action on the file. So, for e.g.
-rwx-rw--r-- 1 someone someuser 20984 Jun 13 10:22 file1
Would mean the owner has read, write and execute permission, the group only has read and write and the world only has read.
You can pass a set of three numbers, each one corresponding to the owner, group and world respectively, to the chmod command to adjust these permissions.
r = 4
w = 2
x = 1
So the command:
chmod 467 file1
Would change the permissions on file1 thus:
-r--rw--rwx 1 someone someuser 20984 Jun 13 10:22 file1
Now you can apply this information to change the permissions on your file to how you desire
As optimus said check the man pages, this is only very basic stuff on controlling permissions.
Regards.