You can find many articles at [SiDoSi (sidosi.org)'s resources page] 1 or at this tutorial on blogspot. Also, I'd recommend a translation of "The second major book about Solresol, written by the other major contributor to Solresol, Boleslas Gajewski," also at sidosi.org over here.
Note that SiDoSi (sidosi.org)'s resources page has an error that requires you to click the
[+] and then the link that appears because the direct links don't work and redirect you. Else see the beta version, without broken links.