To get the Antifreeze to the pump you will need to get it into the tank and then run the pump. I will asume you will be using an RV Antifreeze.
Here's some info on RV Antifreeze from an article I read and below the article is a link to a site that covers the basics of RV water winterizing.
Types of RV Anti Freeze
from J&M Camper and Marine (J&M Camper Sales | Maine's Camper & RV Dealer
RV Antifreeze - Not all Antifreezes are Created Equal
RV/Marine non-toxic antifreeze is probably the most misunderstood commodity in our industry today. There are currently three different varieties on the market.
Ethanol (alcohol) based: This type of antifreeze is most readily available in hardware stores and most RV shops it sells for approximately $3.00 - $4.00 a jug. However, this product is also extremely flammable and not to used around any sort of pilot flames or cigarettes. As well, this product has been known to taint certain RV plumbing systems and is only to be used with Quest or Pex plumbing lines. If you have ever used this product you will quickly remember how bad you water smelt and tasted the next spring. Furthermore, because this product is made from alcohol it works to dry out all the rubber seals readily found in your faucets and toilet.
Propylene Glycol based: This product is only available at your local RV shop (and not every RV shop for that matter). It sells for approximately $5.00 - $6.00 a jug. Like the ethanol antifreeze, this product is non-toxic and safe for all RV plumbing. However, propylene glycol does not have the same fire safety warnings, nor the risk of tainting your RV plumbing system. Furthermore, propylene glycol is a lubricant and will actually work to extend the life of the seals in your faucets and toilets, unlike the ethanol based products.
Propylene/Ethanol Blend: Again this product is non-toxic and completely safe for RV plumbing systems. It will cost more than $4.00 - $5.00 a jug. This may seem like a good idea, however, it is unknown how much ethanol is required to taint RV plumbing lines and dry out plumbing seals.
Here is a link to a site that covers the basics of winterizing RV fresh water systems Winterizing RV Fresh Water System