There’s no way to attach files as you normally would in an email correspondence; however, you can upload your files to any one of the File Managers in Panel and reference the resulting link in your email. This will allow recipients to simply click the link to view/download the file.
Please note that there are multiple file managers within Panel, each serving as a storage for different tools in your panel, but it is recommended to use your Community’s theme file manager since it provides a link you can copy. This File Manager can be found under Panel Functions > Community Manager > Themes > Upload file.
Click here to learn more about managing files using the File Manager.