You start off the game using Marcus and Ed. This is the perfect time to familiarize yourself with the combat controls. Play with the controls and movesets first while everything is quite easy. At this point, the easiest way to kill a zombie is by going up close and hitting with a dropkick (LB + A ), then while they are knocked down press LB + Y for the finisher, you have to have a weapon equipped to do this easier.
After the initial fight , make your way to the Ranger Station. The location is up above when you pull up the map by pressing Back. It's best to sneak your way into it as the game suggests, hold down B to enter sneaking mode and hide through the bushes. Once you've reached it, a cutscene happens.
Now go to the water tower located outside and climb up. Up above, hold down LT, and scan the area horizontally using the LS. Once you see a question mark, hover your cursor above it until it is fully analyzed, make sure to find all marks indicated by completing the searching meter on the left.
Several points will appear, focus on the supplies first while making your way to the Ridge Cabin. Once you've collected and your inventory is filled, go back to the Ranger Station and dump the excess items in the Supply Locker. The large backpacks will help a lot, so use them when you get one. Search silently if there are zombies around, this is especially helpful since you are still starting. After all searching areas are finished, follow the next mission Distant Gunshots.