Fixation is something different, it would mean that you're "attached" to something in an obsessive way. We say "retain information" to mean keeping the information in our heads, so you could say "retention (of information/knowledge)". "Consolidation" would be more like taking several things and putting them together. For example, you consolidate your knowledge of biology, anatomy and chemistry when becoming a physician.

Consolidate means tobring together so do you want to consolidate the lessons together?