I learned by just playing with the program. There is a tutorial in the help file that teach you step by step how to create a new component. Then it use that component to make a circuit with 4 identical parts. It teaches you how to duplicate one part into 4 so you just have to draw the original part one first. There are others that you also learn like making the titles box on the right bottom corner and how to add documentation infos.
It is quite boring just reading the tutorial without any hand-on. You can fall asleep very soon and it is quite tough to imagine what's going on on the screen without actually doing it.
So my advice is: just install the program and go to HELP/tutorial/A guided tour of the ISIS editor... and off you go.
I also have never done any device characteristic graph plotting on the proteus. I have read the help files on the topic years ago and have found no demand for using it.
I mainly use proteus for simulating digital circuits, microcontroller and microprocessor circuits. Those things you want to do are best done on LTSpice and I saw a lot of them being performed on LTSpice here and the AAC forum.