It's a huge shortcoming/fail not to have introduced illi illum illud and eum eorum eos etc. It is like an entire section of tips or more than one, is missing. It's pretty essential stuff. And I checked all the tips it's not further along the course either.
I might just have to report all of these untill that basic piece of grammar is added. Think about learning english and not being taught him his mine me etc. Rather unthinkable. (I should, but probably won't...)
For those that are lost here are the relevant tables that should have been explained in the tips.