Fonts

Instructions on adding fonts/custom fonts are in - texdoc.org

texdoc fontspec

If custom font, you need to save font locally and specify it's path

\setmainfont[
    Path=./fonts/Source_Sans_3/static/] {
    SourceSans3-Regular.ttf}[
    BoldFont =  SourceSans3-Bold.ttf,
    ItalicFont = SourceSans3-Italic.ttf ,
    BoldItalicFont = SourceSans3-BoldItalic.ttf 
    ]