I can't Access NEI, even though I have the mod installed. I can't find the options tab, and the items or the options tab doesn't show.
NEI is meant to be a survival mod (technically cheating) but can be accessed by pressing "O" in the survival inventory. From there, you can press/hold shift to get an infinite stack of whatever (as long as you open your inventory before 128 is gone). To change these, you must go to the "mods" section of the options screen. You can mess around with all the mods you have installed to minecraft. You select "Not Enough Items" and go from there
First and foremost, if you use NEI you need to also have the mod CodeChickenCore to be able to run NEI. After you've put both of them in the mods folder and started a minecraft world, if you're in creative you cannot access it unless you press the chest tab on the bottom right(as seen in image). This tab is almost like your inventory will look like in Survival Mode, except id doesn't have the crafting grid. Once you've opened that tab you should be able to see NEI. If you're in survival, then the NEI will be shown. If it doesn't show in survival, try pressing the "O".