The four simple commands below will get you from 10.1 to 11-current. Depending on your CPU speed, it could take a few hours so be patient.

> svnlite co https://svn.freebsd.org/base/head

> cd head

> su root

> make buildworld buildkernel installkernel installworld && reboot

Notes about 11 current:

https://www.freebsd.org/relnotes/CURRENT/relnotes/article.html