Need to populate Site/Region code

[suraksham]

I have a requirement to populate INC based on the site it was created but first how will i create a multiple select dropdown filter on the site/region code? 
Can anyone Please guide through

[Mark Manders]

What did you already try and didn't work? Adding variables to forms is basic ServiceNow. Just select the correct tables and you're done. What are the challenges you are facing?