Do you already file a schedule D? You would use it for investments, like if you sold stock.
This is what Schedule D looks like:
https://www.irs.gov/pub/irs-pdf/f1040sd.pdf
If you wanted to list each item, this is the form you would use (in addition to schedule D):
https://www.irs.gov/pub/irs-pdf/f8949.pdf
See all the information that is required? Do you have all of it?
You can just file out these forms without using a tax program. Each form on the IRS website has an instructional page also.
I've only done an amended return once. It has three columns for each item. You have to put in the numbers from your original return, then put in your changes. Then you would attach your Schedule D and 8949.
Do they give you an option to do an amended return?
I think at this late date, it might be too much for you to do on your own. Personally I think doing a schedule C would be easier than schedule D and 8949, but getting advice on the internet may not be the smartest. Does the guy who is doing your taxes work for himself or for a company? If he works for a company, maybe you can ask to speak to his supervisor or someone else in the firm.