If you’re using DropBox on your computer then your computer will be linked to a particular account. IF someone else Is using it then you’ll want to connect your DropBox software to another account.
There’s an easy way to do that. Right-click the DropBox icon in the system tray, and then click on preferences.
There, click on the account tab, and then click on “unlink this computer”. Then, you’ll be able to connect whatever account you like.