An attachment is simply an additional file sent with an email message. An attachment can be an image file, a Word document, or one of many other supported file types. When your recipients open your message, they can double-click on the attached file to open it with the program assigned to that file type on their computer. If they do not have a program installed that can open that type of file, they may not be able to open the attachment. Also note that some email providers place limits on the size of the files that can be attached to email messages, while others block certain types of attachments (such as executable files with the .exe extension) to prevent viruses.
Click the icon where the mouse cursor is pointing to select attachment.
This where you select an attachment, by browsing your local file manager. Select a file to attach, by right clicking an item or go to a folder double click to open its content and chose a file to attach on SMS.