To become knowledgeable in global politics, you need to make a habit of reading the world's news daily. Which means, while you should keep up on national news, also regularly check out the "world" section of your media sources. Have a look at the following infographic on news value, reliability, bias and accuracy:
As always, in general, you'll want to read your sources critically. Political bias doesn't necessarily negate the newsworthiness or analytical rigor of a source. But it does provide valuable context for your interpretation of it. For example, Jacobin is dedicated to analysis from a left perspective, which helps to explain its choice of issues, focus, angle, references, and staffing. Because sources in the top, green tier are dedicated more to fact-reporting than those in the lower tiers, they should be central to the mix of your daily news sources. But first, what misconceptions do you have about the world? Check Gapminder:
BBC World Service - Global News Podcast - Downloads
Latest news from around the world | The Guardian
Breaking News, World News and Video from Al Jazeera
World Newspapers and Magazines on your Finger Tip
World Politics Review | Analysis of international affairs and global trends