How do I set my own validator?

The best tutorial can be found here, it also explains how to encrypt your wallet and unlock it for staking only which should be the configuration used. The tutorial is for a Pi3 but it is applicable for linux also.

How do I unlock my wallet for staking only?

>/path/to/wallet/qtum-cli -stdin walletpassphrase
<your passphrase>

Where is my wallet.dat located?

Linux: ~/.qtum/

Mac: ~/Library/Application\ Support/Qtum/ 

Windows: %appdata%/Qtum