As long as the tire size falls in the range of the inner tube, you will be fine. I've still installed a 700Cx28-32 tube in a 700Cx23 tire when nothing else was available. The tire must fit within the range for the rims. Your bike most likely came with 622-15 ERTO, which will fit 700C x 20 to 28 tires.
Find a mentor. Make a list of at least three people that you could approach for help, list your specific needs and then be courageous enough to begin asking.