German is generally considered to be a difficult language for English-speakers to learn, and one of the main reasons is that it is a gendered language. This means that every noun is either masculine, feminine or neutral, all of which are indicated by specific articles and endings.
It can be tempting to ignore the articles when you first start learning German. After all, there are a lot of things you need to remember, and memorizing the gender of each noun can seem like a herculean task. But if you don't, you'll be handicapped later when you start to work with the cases and try to form more complex sentences.
Although it can seem that there is no rhyme or reason to the classifications of noun genders, there are some categories that you can memorize to help you along the way. It is important to remember, though, that many of these categories have exceptions (der Reichtum, das Ei, die Erlaubnis) which you should watch out.
When learning new vocabulary, it's also important to write down the articles for each new noun you use. While this won't matter much at the very beginning, it will be hugely helpful when you advance further in your studies.
One good strategy is to use color coded notecards (blue for masculine, red for feminine, yellow for neutral), or try out this approach proposed by a commenter on DW Deutsch Lernen:
Ich bin jeden Tag frustriert an der Artikel zu erinnern, deshalb habe ich eine Strategie gemacht. Blau-Maskulin, Rot-feminine, Schwarz-neutral. Color Association. Viel Spaß!