eCart 4 Getting Started Guide
The eCart 4 Getting Started Guide can be found here
ecart4_gsg.pdf
Currently the eCart Support page doesn't have an Archived Documentation link to expose these links, but that should be fixed shortly.
One thing to note is that the steps for using eCart 4 vs. eCart 5 have not changed very much, and the eCart 5 Getting Started Guide should work for any eCart 4 user.