When you click on a new skill set (a new circle on the "Learn" page), the Tips & Notes are behind the light bulb icon. Not every skill set has tips and notes, and some courses are better than others in this regard.
For Spanish grammar, this is a good site:
On Duolingo the technical term "skills" is being used to describe themes / topics.
They are the round circles with a given name in your "tree" on your Home/Learn page.
On your Duome progress page it is the list with the (long) names: www.duome.eu/USERNAME/progress
More background about the old html formatted "tips and notes" and the new mobile app like tips:
As your Spanish from English course belongs to the group of new CEFR courses, the new tips (new format/layout/features) are available with the lightbulb button for unlocked (colored) skills, which staff/contractors have already ported over from the mobile app to the web.
Duome introduced a new beta feature with the new notes lately: http://www.duome.eu/notes
See their last blog comment about formatting issues: http://www.duome.eu/blog
I have heard that the last (2) sections in your Spanish tree do not yet contain new tips: https://forum.duolingo.com/comment/31508369