Within Teamwork, you can upload files directly to your integrated storage apps such as Dropbox and Google Drive.
In the Files area of your project, click the File Integrations button in the top right to select the storage integration you want to use.
A modal will open listing the existing files you have access to within the associated file integration. Click the Upload button in the top right.
When you click Upload, you will be prompted to browse and a file from your computer.
Once a file has been uploaded, you can use the checkbox on the left of the file name to select the file and click Link-in Selected Files to link it to your project.
For more information, see: Linking Files from Integrated Storage Accounts to Your Project