How can I find the relevant pathway map from gene-gene or protein-protein interaction list? I have some difficulties to understand/interpret the pathway map and how a gene-gene interaction list or DNA sequencing can map into pathways.

In addition what's the difference between MARK/ERK pathway and the output of KEGG
See a project like Plant reactome, where they infer the pathways of all sequenced plant genomes using orthology to well annotated species.
http://plantreactome.gramene.org/