What is SPOJ?
SPOJ – Sphere Online Judge – is a problemset archive, online
judge and contest hosting service accepting solutions in many languages.
The first thing you need to do is to register
(it's free and spamless). Then find problem from one of the extensive
problemsets, write a solution in your favorite language and submit
it. Next switch to status page
and watch progress of judging of your solution. After few moments you will see the result:
AC - accepted - your program ran successfully and gave
a correct answer (this you will like most :) )
2. WA - wrong answer - your program ran successfully, but
gave an incorrect answer
3. TLE - time limit exceeded - your program was compiled successfully, but it
didn't stop before time limit
These are status codes you will see most often. To know all of them, see
FAQ or this tutorial.
Simply solve more problems :)
To get more familiar with SPOJ read one
of the availabe tutorials or find answer in FAQ.