user@machine:~$ sudo chmod 777 somefile

Examples:

user@machine:~$ touch somefile

user@machine:~$ ls -lh

total 0

-rw-r--r-- 1 user user 0 Mar  7 02:47 somefile

user@machine:~$ sudo chmod 777 somefile

[sudo] password for user: 

user@machine:~$ ls -lh

total 0

-rwxrwxrwx 1 user user 0 Mar  7 02:47 somefile

the permissions are mapped as followed:
Owner Group Other(Everyone)

read write execute read write execute read write execute

rwx rwx rwx

decimal      unix                   binary

770 -> rwxrwx---  111 111 000     

700 -> rwx------  111 000 000

110 -> --x--x---  001 001 000

100 -> --x------  001 000 000

222 -> -w--w--w-  010 010 010

220 -> -w--w----  010 010 000

200 -> -w-------  010 000 000

333 -> -wx-wx-wx  011 011 011

444 -> r--r--r--  100 100 100

356 -> -wxr-xrw-  011 101 110

755 -> rwxr-wr-w  111 101 101

Numerical permissions

#	Permission	rwx
7	full	111
6	read and write	110
5	read and execute	101
4	read only	100
3	write and execute	011
2	write only	010
1	execute only	001
0	none	000