To upload the Natar villages, go to Artifacts -> Leadership -> Artifact villages in the sidebar (if you don't see that, then you don't have permissions - ask your group leaders).
In Travian, go to the Treasury and copy the page with small artifacts (CTRL+A, CTRL+C). In Travco, click the green plus button and paste the Treasury into the container. Repeat the same steps with large artifacts.
You can also use Travco for World Wonder (WW) construction plans - just copy-paste small artifacts from the Treasury, Travco recognises that there are WW plans in there and will upload only those.
Please be aware, than you need to wait until all artifacts are spawned on the server (usually it may take between a few seconds to minutes).
Testing Treasury upload
Testing files for treasury upload can be found below. Please note, that coordinates of artifacts are not representative of where the artifacts may actually spawn.