Problems setting up disks as RAID

I am attempting to install Ubuntu Server 16.04 on RAID. I am using Ubuntu's Documentation to guide me. I repeatedly get stuck at the partitioning stage. I choose manual and then attempt to follow the steps in the Documentation. I am able to follow the steps easily in creating partitions for swap and the remaining space. My problem is that I am never given the option to set the partitions as primary as the documentation states. I have also watched several videos online that show a small window popping up during the process that allows you to make a choice. I never get this window. I am also unable to set the bootable flag to "on."
When I highlight it and press the space bar, nothing happens. I have tried every other key including "enter" without results.

in a previous attempt I just proceeded without these changes, but my system displayed an error when attempting to install Grub.

I am so frustrated, I am ready to pull my hair out. I would appreciate any advise or suggestions on my problem.

Thank you !