You can view all approved devices linked to your Dashlane account by signing in to the web app and clicking on your email at the top right and going to Your Devices tab.
From here, you can see when each device was granted access and by clicking on anyone you can rename the device or disable access. Please note that if you click on De-authorize then you will lose all your data on that computer. This is only important if you don't have sync enabled. With sync enabled, you can delete all of the devices on this list without risk of losing any data.
You need to authorize your computer when you connect to the web app online, and you need to re-authorize your account if you use a different browser or if you empty your browser's cache / cookies. This means that sometimes you will end up with a few duplicates of your computer.
You can use the icons to the left of your devices to tell where they come from. You will see a Windows or Mac sign, a phone or a world (representing the web app).