I have an LLC and using self-employed, what expense category do I put payroll for myself & for one employee I had? Would it fall under other biz expense?

You should see something like the screen in the screenshot below (which was taken from the desktop program) for which you need to answer "Yes" in order to enter employee payroll.

Note that if your LLC is a single-member LLC (you are the only member) and you're filing a Schedule C with your 1040, you do not pay yourself a salary or wages.

put another way, you cannot deduct your salary as a single member LLC that has not elected S-Corp taxation.  if no such election for the SMLLC then hopefully you did not report your "salary" on any payroll tax returns. if you did they need to be amended. 

With a single member LLC reported on schedule C, the owner is not an employee and does not get a W-2.  The owner is taxed on the net profit (income minus expenses) regardless of how much cash the owner took out or left in the business account.   If you have been paying yourself a salary and reporting your withholding on form 941/944, that needs to be corrected.