When preparing a return that contains Schedule K-2 and Schedule K3, there are two ways to include these forms with the e-filing of your return:

Solution One - Automatic Attachment - Set Auto Generate and Attach PDFs to E-Files: 

1. Click the Settings dropdown menu
2. Select Options
3. Within the Setup Tab, locate the option for Auto Generate and Attach PDFs to E-Files to 'yes'
4. Click OK to save these changes

When preparing a return using Solution One, with a Schedule K-2 and Schedule K-3 generating, these forms will be included as a PDF attachment when e-filing.

Solution Two - Manual Attachment: when Auto Generate is set to 'no'

1. Print all generated Schedule K-2 and Schedule K-3 forms to PDF from the forms view
2. Go to the Electronic Filing screen
   1. Partnership - Screen 4
   2. S Corporate - Screen 3.2
3. Click the PDF Attachment button 
4. Select the Attach PDF button at the top of the page
5. Browse to the file location where you saved your PDF forms
6. Click OK
7. Repeat steps 4 through 6 to attach multiple items

For more information, see IRS article:  Schedules K-2 and K3: Interim Electronic Filing for Tax Year 2021