I get gas royalties from three different companies. How do I separate them to show as property A, B and C on schedule E. Do I have to show them as separate properties

Yes, set up three different properties under the Rental Properties and Royalties section of Wages & Income. Be sure to indicate these are royalty properties and use a unique nickname for each one. Then enter the related Form 1099-MISC for each property. (To avoid duplication, do not enter the 1099's under the 1099 topic.)

Additional information: How to Enter 1099 Royalty Income & Expenses