Are you doing this within a map document or outside?
If outside, you need to save a layer file for each one, as the help says
"To save the output layer, right-click the layer in the ArcMap table of contents and click Save As Layer File, or use the Save To Layer File tool."
Otherwise, you can change the environment settings to guarantee geoprocessing outputs are added to the map document, if it doesn't add automatically after geoprocessing.