There are many United Nations documents related to non-self-governing territories, the rights of peoples to self-determination, and indigenous rights. The best way to search for them is to use the Official Document System (ODS). ODS contains the full text of official UN documents, but it doesn't include every document created since the beginning of the UN in 1945.
The Yearbook of the United Nations annually describes the activities of each body of the UN. Use it to find declarations, resolutions, peacekeeping, and other actions.
For more information, refer to the United Nations guide.