How do you learn how to Design?

[Kate Barry]

My sisters and I are inheriting my grandmother's home. She's been here for almost 50 years, its beautiful and has great bones and is in a great location.  We will be doing a lot of work to the land as well - clearing trees for a view, landscaping and rebuilding the gardens and stone walls, etc.  The interior needs to be completely updated, and the layout needs to be changed too.  The basement is a walkout and would be great to finish as possible second unit.  We want the property to have a lot of options.

I really want to learn how to design rooms, in terms of structurally and functionality as well as aesthetic.  What is a good course to start this journey?  I don't have any background in building or art but I'm kind of looking at a winter holed up on top of a mountain and would like to try something totally new and outside my comfort zone just to see if I can do it!