In the Alexa app, this is achieved by selecting the main menu button (found in the upper left-hand corner of the screen) and choosing the Skills option. From here you can browse Alexa skills by category or other criteria such as those favored the most by its large user base. You can also search for skills by keyword or name through this same interface.
You'll notice in the lists below that many Alexa skills are called by using trigger words like open, start, play and ask. While select skills require you to use specific terms, others consider them to be interchangeable and will work with some or all of these phrases. Over time you'll begin launching your favorite skills by the words you feel most comfortable using. Initially, though, it can be fun to play around with each.
The Capital One skill allows you to check your credit card balance or make a payment when one is due. This is secure: The skill performs security checks and requires you sign in using your username and password. Then, when you open the skill, you must provide a four-digit code to confirm your identity. Just be wary of who is around when using the skill -- anyone who overhears you say your personal key can access your banking or credit card info just by asking Alexa.
If you want to do some casual research for a future trip, you can get fare estimates using the Kayak skill. You can say, "Alexa, ask Kayak where I can go for $400" or "Alexa, ask Kayak how much it costs to fly from Los Angeles to Dublin." The skill will ask for additional information and eventually provide you with a series of options and price ranges.