I started by incorporating lettering into my existing illustration projects—as a designer you could do this by offering to letter some headlines for a project instead of using a typeface (if that worked for the project). As far as resources, there are now loads of online classes (skillshare, lynda, etc), and the Type Directors Club is a great place to look for workshops / livestreamed events / book recommendations. I also have a Pinterest board of all design related books if you want to check that out!