Hi Susie,
Just to add to what's already shared, you can also check this article for more information on changing slide sizes in Storyline 360.
Also, I wanted to invite you to our tips and tricks webinars. Once each month at 11am ET, our training team hops on a live call to answer top questions from our customers.
It's super casual (and they're super smart!), so it's a great place to get expert tips and answers to frequently asked questions from our online community. In short, everything you need to create incredible online learning! You can register for the next call here: https://articulate.fyi/3ZiKgu9
And don't worry if you can't make it, because everyone who registers will get a recording sent to them afterwards! There's also a huge list of on-demand past trainings available.
Hope to see you there!