Opendime is a small USB stick that can act as a temporary Bitcoin wallet. You can "top up" with Bitcoin as many times as you want, but as soon as you break the seal, the private key (meaning the password required to access the wallet) is revealed and anyone that plugs in the USB stick, can see the private key and has access to your funds.
OpenDime should only be used as a temporary Bitcoin wallet since you cannot make a backup of it (unless you break the seal). When the seal is broken the funds should be immediately sent to another Bitcoin wallet that you have access to. After the transaction is confirmed and your funds are secured in a safe wallet, the unsealed OpenDime should be disposed.
There is a small hole on the back of the OpenDime with an arrow pointing towards it. If you use a small pin to push through that hole, you will remove a component from the board, causing the OpenDime to reveal the private key and allow you to access your funds. --> Video Demonstration
There is a video that explains and shows the process of accessing your BTC and sending it to your own wallet; both from a mobile device and a computer. --> Video
To top-up your OpenDime with more Bitcoin just scan the QR code that was included in the gift box (if you have no idea how to what I described above, you should probably send me a message). You can also find your public address by plugging in the OpenDime on a computer or phone and opening the text file labelled after the public address.