Provide several perches and a woven nest basket or box nest with appropriate nesting material like dry grass or shredded paper. You can also include some toys or ladders in the enclosure, but avoid too much excess clutter in the cage, which takes away space for flying about.
Keep your enclosure in a warm room free from both direct sunlight and drafts. Make sure the room is warm enough for your Owl Finches—a minimum of 60 degrees Fahrenheit.