The investment in the business or stock sales?
For business loss you just enter your income and expenses. If your expenses are more you will have a Net Loss on schedule C. You don't enter the loss, it is calculated and goes to 1040 line 12.
For investments you should get a 1099B for sales.
Enter a 1099B under
Personal
Personal Income
Then scroll down to Investment Income,
Then Stocks, Mutual Funds, Bonds, Other - click Start or Update
