Elizabeth, it’s quite straightforward, and I’m sure you’d feel confident after reading up a bit!
Have a read of the tool page
https://discourse.southlondonmakerspace.org/t/3d-printer-ultimaker-2/16
How to load filament:
https://support.ultimaker.com/hc/en-us/articles/360012004880-How-to-insert-filament
Using Cura software
https://support.ultimaker.com/hc/en-us/articles/360011837399-Getting-started-with-Ultimaker-Cura