How to use tattva cards?

I tried using these cards but I get no clairvoyance so I guess I must be doing it wrong.

Can anyone who has used them to open the third eye tell me how they use the tattva cards?

You don’t use the tattva cards to open the third eye, or at least, I’ve never heard of them being used for that. In the Western tradition they are used for scrying and for traveling to the elemental realms.