You might like to look at this resource for some Terminal basics:
https://iotgadgets.com/2011/10/enabl...e-11-nokia-n9/

Before typing "aegis-dpkg -i lib1.deb" in Terminal did you specify where to look for it e.g. cd /home/user/MyDocs/?

Presumably by now you have found after devel-su to type default password rootme?

You did apply point (2) at start of thread Settings > Applications >
Installations and enable the option 'Allow installations from Non-Store sources' ?