You can add any amount of collateral to your Wirex credit 
 
To add collateral, simply add funds to your crypto account and you will be able to send funds from your crypto account to the collateral amount. 
 
You can add collateral to ETH and BTC. You need to have a positive balance on one of the accounts to be able to add collateral for the credit to be made. 

Collateral is added by clicking on the Wirex Credit account you wish to fund and hit Add Collateral.