where can I download gcc
 

and how to install it in my ubuntu?

You really should have searched for documentation. https://help.ubuntu.com/community/Programming

in a terminal do: sudo apt-get install build-essential

apt-get install gcc
Read documentation before posting and / or google , because:
1°) UBUNTU inline documentation is really well done, and the packages manager is well explained
2°) If you've googled "gcc ubuntu", I'm sure you would have plenty responses
3°) If you want to increase your linux potential, you'd better to try searching by yourself before asking, especially that many responses are quite simple to find thanks to the web.