You may want to attach a file or files to a specific Task, such as photos relating to a site or more details of contractors/staff relating to that Task. In order to do this, go to the Task/Project list and click on the Task/Project in question. When it is open, you will see a tab slightly down the screen dedicated to Attachments, with a plus (+) button giving the option to upload, as in the below image.
Clicking the add button will open a modal with options to upload either a link or a file from your computer - you can choose from the options on the left as seen in the below image. Here we are uploading a file. When you select a file from your computer, it will immediately upload into the Task/Project.
When the file has finished uploading, it will then appear in the attachments tab on the Task/Project page. Options appear next to the file allowing you to edit the title, download or delete the attachment.
An attachment icon (paper clip) will also appear next to that Task/Project in any lists. This paper clip can be clicked for quick viewing of attachments.