Calendar

To enable access to Calendar while offline

• With an active internet connection, open Calendar
• Click the cog in the top right, then Offline

• Accept the message that pops up, and enable offline
• To view the calendars that have been synchronised for Offline access
• Open Calendar
• Click the cog in the top right, then Offline
• Tick the boxes against the calendars you want synchronised for Offline access

Mail

To enable access to Mail while offline

• With an active internet connection, click the app launcher in the bottom left of ChromeOS
• Find or Search for Gmail Offline, and open
• Select Allow offline mail, then Continue
• To increase the amount of past emails available offline
• Click the cog in the top right of the app
• Change the drop down next to Download mail from the last: to your required setting

Note: You might not already have Gmail Offline installed. Simply click 'Add to Chrome' before following the steps above.

To create a new document while offline

• Click the app launcher in the bottom left of ChromeOS
• Click on either Google Docs, Google Sheets, Google Slides or Google Drawings
• Click the + button in the bottom right of the screen to create a new document of that type

Making non-Google Doc files available while Offline

To make a file that isn't a Google Document, Sheet or Slides file available while you're offline:

• With an active internet connection, click the App Launcher in the bottom left of your screen
• Open the Files app
• Open the My Drive folder on the left, then navigate to the non-Google file you want to make available offline
• Right click the file, then click Available Offline

Further documentation on working offline

Google Drive: https://support.google.com/drive/answer/2375012?hl=en