Well, (you lucky dog) you go about drinking it the same way you would any other bottle of wine.
After it has become wine, there is really not much that can happen to it that will cause it to be harmful to you. The worst case is bacteria have gotten into the wine and turned it into vinegar, in which case you have a great bottle of high end vinegar to cook with.
Hopefully it has been properly stored (on its side) and the cork is not overly dry so it will not crumble when you uncork it. Carefully remove the cork and give it a sniff. Does it smell like wine or smell like vinegar? Pour a small bit in a glass, swirl a couple of times to let breath and so you can look at the “legs” to asses sugar content. Take a good sniff (once again, wine of vinegar?), then take a sip.
Enjoy!