DIY. Replacing toilet. Advice needed

[Dell J.]

I bought a house.  In the process of fixing it up.  I wanted to do some DIY.

In one of the units you can smell the sewer gases when the toilet flushes. I decided to change the toilet and wax ring to fix this. 

When I remove the toilet, what I see looks completely different from What I’m seeing in YouTube videos.  Can anyone give me some guidance?  It seems like the toilet was sitting to high previously. this is my first time doing this.   I put the green plastic bag in the drain.