update asset help

Author: oscarlevin

GenerateAssetsHelp.md

@@ -4,4 +4,14 @@ There are three docker images available trading off between size and functionali
 
 To change the docker image, open the file `.devcontainer/devcontainer.json`, comment out the line starting with `"image":` and uncomment the appropriate alternative line below that.
 
-Once you save the `devcontainer.json` file, VS Code should offer to rebuild your container.  You can also force a rebuild using the command pallet or clicking the "Codespaces" button in the bottom status bar.
+Once you save the `devcontainer.json` file, VS Code should offer to rebuild your container.  You can also force a rebuild using the command pallet or clicking the "Codespaces" button in the bottom status bar.
+
+## Alternative method for getting sageplot support
+
+If you are on the `pretext:small` image, you can also "upgrade" to full by running the following command in the terminal:
+
+```bash
+bash ./.github/scripts/add-sage.sh
+```
+
+To do this automatically when you create a new codespace, you can comment out line 33 from the `devcontainer.json` file, and uncomment line 36.