This document shows how to create an offline wallet that holds your Bitcoins and a watching-only online wallet that is used to view its history and to create transactions that have to be signed with the offline bitcoin cold storage before being broadcast on the online one. The Master Public Key of your wallet is the string shown in this popup window. Transfer that key to your online machine somehow. Paste your master public key in the box.
Click Next to complete the creation of your wallet. When you’re done, you should see a popup informing you that you are opening a watching-only wallet. Then you should see the transaction history of your cold wallet. From file in the menu and select the transaction file created in the previous step. Once the transaction is signed, the Transaction ID appears in its designated field. Press save, store the file somewhere on your computer, and transfer it back to your online machine. The transaction will be broadcasted over the Bitcoin network.