Remember you can usually achieve this from the console as described in @sc-steemit's article and linked by the OP here. Be careful when editing your config file. In fact, everyone should read the linked article anyway as it contains a lot of good practice we should all be aware of. A note on encrypting before you all fly off and do it:

• If you encrypt your wallet, all prior backups become useless. Make new ones.

• If you forget your encryption key, gg no re.

That being said, it is good practice to encrypt your wallet and only unlock it for staking.