need help with tuplets

Hello, I'm new to Notion but have been using Sibelius for 14 years. I'm trying to figure out tuplets, and I'm not succeeding. I've read every forum post I could find, and the manual about 30 times, and tried watching the Notion youtube video (which was awful, unfortunately), and no luck.
I really just need a step-by-step guide to getting mixed rhythms in tuplets. I can occasionally get quarter-eighth triplets to work, but I don't really get why it works and doesn't. I also can't at all figure how to do dotted eight-sixteenth-eighth triplets. I figure if I can understand those two really basic ones I can figure out more complex ones.
Help would be enormously appreciated! Thank you.
I really just need a step-by-step guide to getting mixed rhythms in tuplets. I can occasionally get quarter-eighth triplets to work, but I don't really get why it works and doesn't. I also can't at all figure how to do dotted eight-sixteenth-eighth triplets. I figure if I can understand those two really basic ones I can figure out more complex ones.
Help would be enormously appreciated! Thank you.