Insufficient information to use ISIS from Getting Started pages. #139
Description
Documentation Topic
When someone is looking through the Getting Started > Using ISIS First Steps docs, they should encounter the information they need to actually install ISIS and download or use SPICE data. Some of this info is in the FAQ, but this is info that should be preemptively given before people get confused.
Lessons-To-Be-Learned
How to Install ISIS, How to install SPICE Data/use web SPICE for ISIS.
Illustrative Task
We have docs that illustrate these tasks, but our current (lack of) navigation provides poor means for beginners to find them. Add navigation and links where relevant (In particular, Introduction to ISIS and Adding SPICE under Getting Started > Using ISIS First Steps)
Related to #81