There are many ways to learn. Attending a training course, reading a book and using the Internet are just 3 ways. However another, more informal way is just by talking to somebody. Everyone has something to offer but how do you find these people? Within an organisation, especially a large organisation it’s often via word-of-mouth and reputation. “Bill is our Finance expert, go and have a word with him”.
These days you’re more likely to have better luck if your employer uses SharePoint, Yammer or a similar system that has a “social” element to it. I mention SharePoint and Yammer because my current employer uses both (and with Microsoft now owning Yammer, there’s an expectation that elements of this system will be integrated into future versions of SharePoint).
In Yammer and SharePoint, users can create their own “Profile” which includes a short biography, their interests and an “ask me about” section. So if I want to be seen as the “go to guy” for Excel, VBA and iPad, I add these keywords to my profile and whenever somebody searches on these words, as well as documents and conversations, the search results also includes myself (and anyone else with these keywords in their profile).