Already found your private posting key?
In eg hive.blog UI, you can find all your private keys (including the posting one), under Wallet and then under Keys & Permissions. To reveal the private keys you have to use your master/owner key, likely the key you've used so far to log into HIVE based services. This page also explains the differences between the four private keys you have. For normal usage, the best key to log in to HIVE based services is the blogging key. When handling financial transactions, you may need the active key, but better to use that one only when you need to use it.
All sort of information can be found in FAQ of HIVE, but maybe better to search through the posts and comments on the hive chain. Use hivesearcher.com for that. HIVE post/comment only search engine.
Thanks. I found it all.