1.Downloading
Choose one of these mirrors to download
SA-MP 0.3z Client Mirror by gta-sa-mp.de forums
SA-MP 0.3z Client Mirror by littlewhiteys.co.uk
SA-MP 0.3z Client Mirror by SA-MP Team
SA-MP 0.3z Client Mirror by Everystuff server
(Can be also found on http://www.sa-mp.com/download.php)
2.Running the installer
A link will appear on your browser after you choose a mirror, press it
3.License agreement
Press Agree to continue
3.Choosing directory
After you press "Install" it will take a few moments to install it.
4.Finishing the install
Now just press "Finish" and you have your SAMP updated, you can log back in game now.
Notes.
Make sure you have your SAMP application not opened whilst installing, otherwise it won't let you.