What income do you have? Like W2 or 1099NEC or 1099Misc etc? Are you asking how to enter your self employment income without a 1099NEC or 1099Misc form?
Just enter it as Other self employment income or as Cash or General income. You don't need to get a 1099NEC or 1099K. Even if you did you can enter all your income as Cash. Only the total goes to schedule C.