Volts are claimed along with XP after you complete a quest. Claiming Volts does not require submitting a transaction to the blockchain, but will require that you sign with your wallet to prove that you own the address.
This means that claiming Volts can be performed on any network available on Zapper.
Claimed Volts are accumulated off-chain, and the amount of claimed Volts you have accumulated is tracked in the "Pending" section at the top of the Quests page.
In order to use the Volts for crafting and minting a Zapper NFT, the pending Volts need to be moved on-chain to the Ethereum network. This is what we mean by "syncing." Once the Volts are synced on-chain, they can be used to craft and mint a Zapper NFT.
Visit the Crafting & Minting section of the FAQ for more information on how to craft and mint Zapper NFTs.