Settle
Settle (colony) in the Stellaris encyclopedia: To Settle is when a Arkship permanently settles on a world, ending its nomadic voyage.
Settle in the game's words
The encyclopedia entry as the game shows it in its tooltips; underlined words open their own entry or page here.
To 
Settle is when a 
Arkship permanently settles on a world, ending its nomadic voyage.
This requires that either the Adaptability or Versatility tradition tree has been completed.
To Settle, either select an Arkship and right-click an uncolonized Habitable World or click the Colonize button in the 
Colony View.
An empire with additional Arkships can choose to let them continue as nomads and turn the newly 
Settled Empire into a Subject.
Waystations in unowned 
Systems are converted into Outposts.
More in Colony
Source: common/game_concepts (concept_arkship_settle, also concept_arkship_settling) and localisation/english, Stellaris Cygnus v4.5.2 (9776).