8453 is just a cover sheet, print it and fill it in, and mail along with the 1099B details for the items triggering it.
this is being triggered if you entered sales summaries for 1099B with adjustments (most commonly wash sales, AMD), or non-covered categories etc. if you didn't file already and it's not many entries you can avoid the mailing by splitting up the 1099B and entering these items as "One by One" which will file the details electronically on Form 8949, and enter the balance of your 1099B as Summary level without adjustments which will be reported on Schedule D Lines 1a/8a, and check totals.