Hi Linda
I hope you mean the fiscal year, not the fiscal period!
The only crucial question that you need to get right when creating a GL is how many fiscal periods are in the year - 12 or 13. Unless you are absolutely sure the answer is 13, then pick 12.
After you create the GL, it's easy enough to go into the fiscal calendar (Edit | Fiscal Calendar) and modify the period dates and descriptions. Tedious, but easy.
I hope you found the create button for AP and AR. If the datasets share certain tables (terms, banks, account sets, billing cycles) or form specs, it is possible to copy them from one to the other, but you have to know the file names, which is beyond the scope of your question. You CAN'T just copy over vendors or customers, though, they must be exported/imported.
Steve