I am having some land subdivided to build on, and the orig property has 2 wells, one which is not being used. If it is viable, how would I get water from that well to my house, to avoid digging another well? I would first check with the proper authority to be sure of the legality and than notify the present property owner (if any) of course, before any work was attempted.
One method would be to subdivide in such a way that you own the well - kinda like a gerrymandered congressional district. The other would be some form of right-of-way - but that does veer off into legal questions we don't address here, so I won't go there. But that assumes many things about its worth that we don't know; Many of which you probably don't, either.
In many cases the presence of two wells on a property, one unused, indicates that the (apparent) "spare" was the first, unsuccessful, well and is disused for a good reason.
Depending on how far the well is from your building site, the cost of trenching and supplying power to the pump can greatly exceed the cost of a new well. Trenches are not cheap, and neither is wire, especially if it has to be large wire because it's a long run. There are many good reasons to keep the connection to the well short and sweet (I kinda liked the house that actually had it in a small extension of the basement, though that can be somewhat difficult to arrange.) If it's a long way from the well to the house there are many more things that can go wrong, simply due to the length of the run providing more access to modes of failure.
To get to the meat of your question, in practical terms, assuming the legalities we don't get into are covered, and the well is worth anything (that's a big one) you have a long trench dug to a depth below (ideally well below) frost line and install pipe (possibly of a larger diameter than you might otherwise use due to length of run) and wires or conduit, and wires in conduit (also possibly of a larger diameter than you might otherwise use due to length of run.) You connect those pipes and wires to the pump in the well on one end, and your plumbing and electrical supply on the other. Backfill with sand for at least a foot, and place tape over the wires indicating Buried Electrical Line Below - refill to within 6" of the surface and place another line of BELB tape just below the surface, then fill to grade.