There are several things you can do if you need more space on your Dropbox account.
How to earn free space
To earn free space, you can Complete the Dropbox getting started checklist or Refer your friends, family, and coworkers.
Note: Sharing a folder doesn't count as a referral.
Upgrade your account
If you have a Dropbox Basic account, you can upgrade to Dropbox Plus to get 2 TB of space or Dropbox Professional to get 3 TB of space. If you have a Plus or Professional account and work with two or more colleagues, you may want to consider upgrading to Dropbox Business, which comes with 5 TB of space.