When you first create the asset, make sure you save it as, for example, my_first_asset.otl, in $HOME/houdini9.0/otls. This way you can have access to the Digital Asset yourself. Then, you can send the my_first_asset.otl file to anyone.
or if you already have created a digital asset, you can save it to a new OTL file by specifying the new file path in “Save to Library” field in the Type Properties dialog