You should always take a gravity reading of your must BEFORE you pitch your yeast. Then, subsequent gravity readings will tell you if your wine if fermenting. You may also see some physical activity, but you can't count on that to tell you what's really going on.
Even if you miss the initial gravity reading, take one now. Then take one in a few days. If the second reading is lower than the first, your wine is fermenting. If it is at or below 1.000, you are just about done with fermentation.