If it's pretty grungy/gooky, you'll need to scrub it first - I'd put a bit of water and detergent on it and get working with a scrub brush. I know water and detergent aren't good for the wood - I certainly wouldn't soak it - but the grunge has to come off. Vinegar might also help.
Once it's dry, use oil as suggested above. Some may say to put on some kind of finish like varnish etc; if the goal is to use it, you won't want anything non-edible to end up in your food.
I definitely wouldn't cut raw meat on it, but I wouldn't hesitate to cut vegetables and fruits and bread - that's what a cutting board is for! Yes it will get scratches, but to me that shows a well-used and well-loved item.
I have a wood cutting board that is at least 50 years old. I use it every day, wipe it down with a damp sponge, and occasionally dunk it in a sink full of water and bleach for a few minutes. I don't bother with the oil though I probably should. My father was the cook in our family and this was his favorite board. I often think of him and his joy in cooking when I use it and see the many many cut marks and dings.