Short answer: Through Buffer.
Long answer: Google still has not made G+ pages writable by external applications except through special approval. A few companies that predominantly do social media sharing and have large user bases have been granted approval. Companies like Buffer. We’ve applied for access, however until we get it, we have to work around this limitation.
(Note: there are a few plugins etc that do this – but they do this through web scraping and posting, which is a violation of YOUR account terms if you use it. Be aware that using them could jeopardize your G+ pages. We recommend against any plugin that claims to post to G+ – they’re not doing it legitimately. If you’re in doubt – ask the plugin developer if they are using the official G+ API or not.)
So – to publish to G+ from Spokal – open a free Buffer account, connect your G+ page to it (don’t connect Twitter, LinkedIn or Facebook or you’ll get duplicate postings), and then connect that Buffer account to Spokal.
It’s a 5 minute detour, which we apologize for, but once it’s setup, it’s just as automatic as everything else, it’s a one-time only thing!