Assassin's Creed Odyssey

You will get progress towards the Knowledge Sequence from completing certain activities, such as main story missions, scanning Isu Data Caches and finding Keeper's Insights, as well as from various other activities and from interacting with Isu writings.

There are 3 levels of the Knowledge Sequence and you need to reach each level to unlock some areas as they are sealed off by level 2 and 3 Knowledge Sequence requirements.

The best way I found to do this was to complete any missions I had, then if my knowledge wasn't high enough, do some exploring to scan Isu Data Caches or find the Keeper's Insights to progress it further and unlock more missions.

This achievement will come naturally from playing the game and exploring the areas required to be explored for the miscellaneous achievements below.