To install ddml from Github:
net install ddml, from(https://raw.githubusercontent.com/aahrens1/ddml/master) replace
To install the development version (not recommended):
net install ddml, from(https://raw.githubusercontent.com/aahrens1/ddml/dev) replace
To install an archived version, use for example:
net install ddml, from(https://raw.githubusercontent.com/aahrens1/ddml/v1.1) replace