add further description

docs/source/Lines_functionality.ipynb

@@ -52,7 +52,11 @@
         "id": "WBD3_FSbOysM"
       },
       "source": [
-        "### Bottom Data Reading"
+        "### Bottom Data Reading\n",
+        "\n",
+        "To start this tutorial, we first download EVL data from Echoregion's github repository and parse the EVL file using Echoregion's `read_evl` function. \n",
+        "\n",
+        "The parsing is based off of the EVL data description shown on Echoview's website: https://support.echoview.com/WebHelp/Using_Echoview/Exporting/Exporting_Data/Exporting_line_data.htm."
       ]
     },
     {
@@ -101,7 +105,7 @@
       },
       "outputs": [],
       "source": [
-        "# Store the object's data in a dataframe\n",
+        "# Grab lines dataframe\n",
         "lines_df = lines.data"
       ]
     },