If you want to use our service you should sign up an MetaMask extension so you can make Ethereum transactions via regular websites. You will have to register in MetaMask system even you already have an ETH wallet, but you can add your wallet after the registration. Visit https://metamask.io/ and select a browser you want to use.
Then you will be asked to add the extension and enable permissions for it, please do it.
As a result you can now see MetaMask icon in the top right corner.
Click on it. then follow the instructions. If you don’t have an Etherium wallet just follow the registration steps. After you finish you will always be able to copy your wallet address from the extension.
If you want to add your existing wallet to the MetaMask simply click on the icons shown on the screenshot below
After that fill in your private key and click on import
After these steps you will be able to switch your added accounts by clicking on this icon