Hi, I'm trying to find out where I add sublease income from my business rental

[RichardK]

If the reason you are subleasing is because you have extra space and want to subsidize your rent payments, then I would suggest you report the sublease income on Schedule E Supplemental Income and Loss(rental income), and allocate a portion of the rental expense from your Schedule C Business Income and Expense, to the rental income (Schedule E).

For example if you sublease 20% of your business space, allocate 20% of your rental expense to the rental income. 

For more information click on the following links:

IRS publication 334 Tax Guide for Small Business, IRS publication 17, Chapter 9 Rental Income and Expenses