How do I report the sale of comic books?

Did you sell them less than you paid for them?  If so, then you do not have to report the loss on a tax return.

If not, and you sold then for more than you paid for them then you have to report the gain on the sale on a tax return.

To enter an investment sale -

Click on Federal Taxes (Personal using Home and Business)
Click on Wages and Income (Personal Income using Home and Business)
Click on I'll choose what I work on (if shown)
Under Investment Income
On Stocks, Cryptocurrency, Mutual Funds, Bonds, Other (1099-B), click the start or update button

Or enter investment sales in the Search box located in the upper right of the program screen. Click on Jump to investment sales