Here comes the simple 12 step guide for you to update C/2012 S1 ISON on your Stellarium.
Pictures on the left side are carrying some arrows with associated numbers. Find bellow the specific step against all these numbers or corresponding arrows.
Example - For arrow with a number 7 read the text of STEP 7 on right side of that image.
Initial Step : Click on the Configuration window icon from the Stellarium. Or press F2.
STEP 2 : Now Select the Solar System Editor from side menu as shown on the picture.
STEP 3 : Click on the Configure button at the bottom of that window.
STEP 5 : Now click on the button Import orbital element in MPC format from the bottom of that window.
STEP 7 : Now write C/2012 S1 at the search field as shown on picture.
STEP 8 : Then click on the Search button as shown on picture.
STEP 10 : Also Select the Radio Button of the C/202 S1 (ISON) option as shown on picture.
STEP 11 : Now click on the Add Objects button at the bottom of the window.
Now you are done with your updating.
Restart Stellarium & search ISON using the key word ---- - C/2012 S1
Have a Happy Comet Observing ....... ENJOY THE SKY WITH SWAN .