I have never owned a horse, but I have dogs. The principle is the same. I can fill their bowls with water and I can show the dogs where the water is located. Until they have a thirst, they won't drink. We are called to share the gospel, it's not our job to force them to receive the gospel, but it is our job to lead them to the water to make sure that they know when they're thirsty where the water can be found.
Matthew 28:19-20 (ESV)
19 Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit,
20 teaching them to observe all that I have commanded you. And behold, I am with you always, to the end of the age.”
Show someone where the eternal water may be found today!