Whether your account is in the Polkadot extension or created/added directly on the Polkadot-JS UI, you'll need to use the Polkadot-JS UI interface to send funds, as well as issuing any extrinsic. The Polkadot extension is an account manager, not a wallet, so it requires a UI to interact with.

In order to withdraw DOT from your account and send funds out, click on Transfer in the Accounts menu, or click on the Send button next to the account you want to send from. 

Both options will take you to the following pop-up window in which you can enter the destination account as well as the amount you want to send. (If you clicked the Send button to get here, then the "Send from" account will already be set.)

For the receiving account, you can either select an account from the drop-down menu, which lists all your accounts and all the accounts in your Address Book, or you can simply paste an address. This field looks like it is just a drop-down menu, but you can actually also paste an address there, so the receiving account doesn't have to be in your Address Book.

Once you have entered all the details, click on the Make Transfer button. This will take you to the pop-up window shown below, which will display your expected transaction fees in milli DOT.

Important Notes: 

  • The transaction fees will be deducted from the leftover funds in your account. If you don't leave enough funds in your account for the fees, your transaction will fail due to "insufficient balance". If you want to send ALL of your funds out, learn how to do that here.

  • Also, you need to leave more than the existential deposit of 1 DOT in your account, if you want to keep it active. If you encounter the error balances.transferKeepAlive click here to learn what this means and how to troubleshoot this.

Once you're ready to make your transaction, enter your password and click the button "Sign and Submit".

If you are using the Polkadot extension, the password field will not appear here, but in the window that will pop up once you hit the Sign and Submit button. Enter your password and then click the Sign the transaction button.

Congratulations, you have successfully sent your funds out! 

You can now open any of the block explorers to view your transaction.