Pay X To Access Gallery And Get X Free Images

Hi .  Sorry if this has been asked before but i cant find an answer.

I want people to pay to use a gallery say £5

This automatically allows them access to 1 free digital download and then purchase any other products as normal.

I set the gallery up with a password, and the customer pays the fee.  They receive the password via email .  £5 for example is invoiced to them.  all ok so far.

How can they download their free image?  This is where im struggling?

might be something to do with either credits or photo products but manual is not clear to me.  examples to my site

Thanks

This is what i see on orders.

thanks

You can use the Download Credits option. Say you make your large download 1 credit to download. And if you include 1 download credit with the purchase of access, they will have the 1 credit on their account to use.