Approve

On the blockchain, an Approve action needs to be taken before further interaction will most protocols. This is an approval for the respective protocol to move your tokens. (read more here)

This applies to both Volorca as well as Uniswap.

For both Volorca and Uniswap, Approve buttons will be shown where approvals are required.
Clicking on these will take you to a Confirmation pop-up from your web3 wallet.

For example, in Metamask, you might see:

You may enter a custom number under the "Custom spending cap".

If you trust the protocol you are interacting with and do not want to have to perform this Approve transaction again, set the number by clicking on Use default.