I'm new to Ubuntu and dual booting multiple OS's. I'm pretty noob in general so please bear with me. I've searched around for a few hours and couldn't seem to find what I was looking for, or couldn't understand the answer. Apologies if this question has been answered before.

About two months ago, for the first time, I installed Ubuntu and was dual booting using the rEFInd boot manager to select either Windows 8 or Ubuntu. I had to go through a bunch of steps like disabling secure boot, switching boot modes, etc etc on my Toshiba to get it to work properly. I don't really remember everything I did to get it to work. 

Last week I did the free upgrade to Windows 10. Now when my computer boots the rEFInd boot manager does not show up, and I don't know how to access Ubuntu. 

* After updating Windows 10, the installation should not have touched
the partition on which Ubuntu was installed, correct? Or do I need to completely reinstall Ubuntu?
* Therefore, it is just a matter of fixing the boot to enable me to  

choose between OS's, right?
* If so, how do I go about doing this? I do not see an option in BIOS to disable secure boot now.

This thread seemed pretty close to what I'm asking, but I couldn't quite make sense of it:
[Ubuntu 12.04 no longer boots on Toshiba Satellite after Windows upgrade](https://askubuntu.com/questions/437985/ubuntu-12-04-no-longer-boots-on-toshiba-satellite-after-windows-upgrade)

This seems pretty close too, but it seems to be giving me commands for an Ubuntu terminal, which I cannot currently access:
<http://howtoubuntu.org/how-to-repair-restore-reinstall-grub-2-with-a-ubuntu-live-cd>

Thanks in advance!