First, be aware of the 21 fonts provided by the ConTeXt distribution's Fonts.
If required, you can regenerate the font database:
mtxrun --script font --reload --force
How to use the fonts included by default in the distribution
\setupbodyfont[dejavu] \setupbodyfont[dejavu] \setupbodyfont[dejavu] \setupbodyfont[dejavu] \setupbodyfont[dejavu] \setupbodyfont[dejavu] \setupbodyfont[dejavu] \setupbodyfont[dejavu] \setupbodyfont[dejavu] \setupbodyfont[dejavu] \setupbodyfont[dejavu] \setupbodyfont[dejavu] \setupbodyfont[dejavu]