even more explicit about channel selection

Author: mrariden

notebooks/run_Cellpose-SAM.ipynb

@@ -225,7 +225,7 @@
         "\n",
         "- If you have a histological image taken in brightfield, you don't need to adjust the channels.\n",
         "\n",
-        "- If you have a fluroescent image with multiple stains, choosing multiple channels may produce segmentaiton of all the structures in the image. If you don't want to segment all the structures in the image set the channels that you don't want to be segmented to `None`, below. "
+        "- If you have a fluroescent image with multiple stains, you should choose one channel with a cytoplasm/membrane stain, one channel with a nuclear stain, and set the third channel to `None`. Choosing multiple channels may produce segmentaiton of all the structures in the image. If you have retrained the model on your data with a thrid stain (described below), you can run segmentation with all channels. "
       ]
     },
     {