After selecting a Currency wallet you can send funds by clicking the 'Send' button on any address that has funds available. If you do not have any currencies on your BC Vault yet, see Can I transfer funds from an exchange or other service to my BC Vault?.
The send popup will look different depending on which cryptocurrency you have selected, here we see the user preparing to send an ETH transaction:
The user is presented with a field for GAS LIMIT and GAS PRICE, which are unique to the Ethereum cryptocurrency (and all ERC20 tokens). To learn more about Gas and the Gas Limit, see What is Gas Price and Gas Limit (ERC20)?.
For other crypto such as Bitcoin, Litecoin, Dash, and Dogecoin, no such field exists, only the transaction fee is shown. Once you have entered all the fields correctly, hit send, enter your password, verify all the transaction details on your BC Vault (very important security step!) and the transaction will be broadcast to the global blockchain network for confirmation.
Transaction fee can also be entered manually (instead of using the sliders). You have to enable Advanced Mode in Settings and then enable "Manual Mode" in top right corner as seen on the example above.
Transaction fees go to miners of particular blockchain and the height is dictated by blockchain itself. For more information see: What are Fees?