Below is a quick summary for BIG-IP Cluster Upgrade

1- force-offline the standby unit
2- import the  new release
3- install the new release
4- reload after installation
5- online the standby unit
6- force-standby the active unit
7- force-offline the standby unit
8- import the  new release
9- install the new release
10- reload after installation
11- online the standby unit
12- review cluster configuration