There will be one or two allen-keyed bolts that attach the saddle to the seadpost. Loosen them, put the seat where you want it and tighten them. On some seatposts, the bolts need to be quite loose before you can swivel the nose up or down. After you tighten the saddle back down, do your darndest to move that saddle forward and back and side to side and up and down with your hands. If you can't move it no matter how hard you try, ride with confidence.