oh, so that's how you Americans do it. We mark it as Kn
Anyways, there are four things to keep in mind:
a) no electron can be in more than one whatever-you-call-them (the s1, s2, etc.), so the sum of all the 'n's must be equal to the number of electrons the atom has (in most cases, Z, or 1 for H, 2 for He, etc.)
b)the final whatever-you-call-them has all the valance electrons, so the number of electrons in it = the number of valance electrons (topology, yes, but it's easy to forget this)
c) the first "s1", or K, as I would call it, has 2 spots where electrons can go, the next 8, and I can't remember the rest, though if you're just starting to learn about this, you probably only need this. The second-to-last s always has the number of electrons "left over" from the previous 's's, minus the number of valance electrons. (1 for group 1, 2 for group 2, 3 for 13, 4-14 5-15 6-16 7-17, and I haven't yet learned about the rest: I'm only in 8th grade)
d) you can't add any electrons to the next 's' if all the previous ones aren't filled (the exception is the last 's', which must hold all the valance electrons)
If anything is unclear, please tell me what, and I'll try to rephrase it.