The process is pretty much the same for all email programs:

• Open a new email message window, usually by clicking the "New Message" or "Compose Email" icon or the CTRL + N keyboard shortcut.
• Click on the menu item with a paperclip icon that says "Attach a file" or something similar (e.g., "Attach Files")
• Browse through your computer's folders and click to select the files/folders you want to attach. In most cases, you can select multiple files by holding down the CTRL key while clicking on each file.
• Click the "Open" or "Choose File" or another similar button to attach the file to your email.
• Then continue composing your email (put the email address of the person you want to send the attachment to in the To: field, add a subject and message in the body, and hit Send).