Even after reading this excellent answer at How do I install Ubuntu?, I still do not know how to get over the partition problem.
Because there is no "edit" button.
Rakesh Godhala said:
In sb4, there is 480 GB disk space, you can create required space from that partition
This is what I do:
Click the sb4.
Click "change" button. (there is no "edit" button for me to hit)
Select as shown:
Click "OK", and then I get the following:
You can see the sb4 type is changed to ext4. and I dare not click "continue", because I fear it will erase my Windows 8. Also, it did not ask me to set space size, I think this is the wrong step.
And I get stuck. So what should I do?