To share a macOS folder with a Windows virtual machine perform the steps below:
1. Open a virtual machine configuration > Options > Sharing > Manage Folders...
2. Click on the + button and select a target folder > Click on Open > OK.
3. The shared folder will be presented as a shared folder under the Custom folders section.
If a shared folder is not visible in Windows try following the steps below that might help you to resolve the issue:
1. Reinstall Parallels Tools. More information might be found in KB 4841.
2. Make sure that your virtual machine isn't isolated:
3. Click Manage Folders... in the virtual machine configuration > Options > Sharing > make sure that at least one of the checkboxes under the General part is checked in the virtual machine configuration.