How to fill KYC level 3? The requirements are for proof of address and source of funds but there is no concrete information about list of documents.
Proof of address is actually some letter that contains your address and most exchange or casino accepted "Electric or Water" bills contains your address under your name of course. For source of fund, maybe you can use salary payment info from your office.
You can freely to ask on "Live Chat" they're open 24hours, so better result always ask to the support.