Currently it is hard to mint WTC - check out the website which lists more detail, but you have to convert ICP to cycles in your cycles wallet, and then you need to send that to our token contract to mint WTC.
We are working on a simple minter tho, where you can just send ICP to a canister and it will automatically convert it to ICP. Once that is up and running it will be very simple to top up using WTC.
We are also adding a feature into Stoic (it was in an earlier version) where you can topup canisters using ICP directly (so you enter the canister ID, an amount of ICP and it will convert it and send the cycles).