2 May 27, 2017 12:33
Please check this pages: http://b2evolution.net/man/upgrade-instructions, or all the upgrade section in general. They will give all the info you need to upgrade your site.
It's written in the manual, but I want to stress this out a bit more before yo start:
- Double check that you have a full backup (code + database) of your site
- Make sure that you know how to restore the backup if things are going south.