Tier 1 Planetary Ports (Planetary Outposts) are the dockable planetary settlements not in a giant ring layout.Is the Tier 1 an outpost? Please tell me what I'd need to craft.
Fly down to a planet surface and fire off the colonisation suite to get the construction menu up for those.
There are three types - Civilian, Industrial and Scientific - each of which has a few layout options.
Tier 1 installations are undockable themselves but a cheap way to get Tier 2 points and give other benefits to the system properties. Some of them are also prerequisites for more advanced construction. They take up a bit of orbital space but unless you have a tiny system there's probably space for a few.
DaftMav's spreadsheet is a good summary of the options https://docs.google.com/spreadsheet...b3a8dmqVqq2o/edit?gid=294937936#gid=294937936