You need to wait until the moisture content in the floor has dropped to less than (approximately) 15%. I don't know the precise value off hand, but perhaps you can find it on the Internet. If you enter "concrete moisture painting" into Google you will find several articles that have been written by paint manufacturers on this topic. You should also be able to find more details at the Concrete Institute. It is important, however, that the concrete be sufficiently dry before you apply the epoxy. This might take more than one week, but will depend on the concrete mix, the local weather conditions, etc. In the meantime, I strongly suggest that you don't walk or drive over the concrete so that you won't need to remove grease and oil before painting.