What are the steps to establish an academic journal?
This question is indeed rather broad. The specific questions you ask are at once basic and easily researched (you can get basic information about ISSN, ISBN and DOI on Wikipedia, for example) and quite complex (indices have their own rules). This leads me to think that you don't know what you don't know.

I suggest that you contact 


A managing editor or production manager of a journal in your field
The publication liaison of your learned society
The acquisitions or new projects person at one of the big journal publishers like Elsevier or Wiley


Good luck.