There appear to be no packages for iosevka for debian. The prescribed method is to add the fonts to the fonts folder. The github issues point towards a PPA which can be added. However, this did not work for me, and I had to resort to manual means.
Downloading the specified font version from github into a temp folder
cd ~/temp
wget "https://github.com/be5invis/Iosevka/releases/download/v2.2.1/01-iosevka-2.2.1.zip"