Here are 2 simple ways to get some initial content going:

I'd say start by getting out your camera and interview the people at your firm and let them tell (funny) stories about subjects relevant to what they do at the firm.
Edit the content into a series of short videos.
Set up a youtube channel if the firm doesn't have one already.
Embed the videos onto the company's site (preferably its blog).
Ask the people in the company to share the content on their social networks.

then

Draw up a list of customer's FAQs.
Take each FAQ and use it as a chapter for a content episode
Write an article for each FAQ and maybe also add a video version.
Publish on website
Ask the people in the company to share the content on their social networks.

They key to getting your colleagues to promote your content is by making stuff they can be proud of, the best way to do that is by featuring them in the content.

Happy to discuss more on a call.