See the map...
It's located on the strategic command height near of strategic highway #1 about a third of the way between Jerusalem and Tel Aviv. You can't miss it, even if you want....
You can get buses ##433, 434, 404, 460 (~ 20 shekels about 20-25 minutes) at the CBS in Tel Aviv or Jerusalem. Or drive by rented car by strategic highway #1 till the junction with Highway #3, and then see the next map.
The green line on the map is in general the boundary of the Palestinian territories under the agreement of 1949. It is sometimes seen as remnants of rusty barbed wire on the ground. No problem for crossing.