chmod
Syntax: chmod 755 swamprocks

Changes the permissions (or mode).
Here, the user (owner) is being given executable privileges on the specified filename (swamprocks) or directory. The three permissions are read, write, or executable: who may view, modify, and execute the file, respectively. The three groups who for whom this is delegated are the user, who is the owner of the file, the user's group, and all others.

chmod         permission             your-script-name
Examples
$ chmod     +x         your-script-name
$ chmod    755        your-script-name

Options Type A

rwx rwx rwx
 |   |   |
 1   2   3

1 – owner
2 – group
3 – others

For r,w,x octal value is 4,2,1 respectively.
So if you want to give r,w,x permission to owner, for group r,x, and for w,x to others. Then,

rwx rwx rwx
421 401 021

For owner add this number as 4+2+1 = 7
For group add this number as 4+0+1 = 5
For others add this number as 0+2+1 = 3

So command will be $ chmod 753 filename

Examples
$chmod 755 first.sh

Options Type B

chmod {u|g|o|a} {+|-} {r|w|x} {filename}

u - User who owns the file
g - Group file owner
o - User classified as other
a - All other system user

+ Set permission
- Remove permission

r - Read permission
w - Write permission
x - Execute permission

Examples
$ chmod u+x,g+wx,o+x myscript

Above command set permission for file called 'myscript' as User (Person who creates that file or directory) has execute permission (u+x) Group of file owner can write to this file as well as execute this file (g+wx) Others can only execute file but can not modify it, Since we have not given w (write permission) to them. (o+x).