Where do I enter salary paid from business to my minor child?

[ColeenD3]

If you have a Schedule C, you would enter all wages on Line 26 Wages (less employment credits).

Please see Schedule C.

[AmeliesUncle]

Don't forget that as an employer you also need to issue and file a W-2, file Forms 941 or 944, possibly a 940 and possibly state requirements.