One of the best ways to enhance the experience of your spot learning content is to add audio. But like anything else, audio can be done well or it can be done poorly...and poor quality audio is distracting. You want the learning experience to be enhanced by the addition of the audio; you don't want the audio to take center stage because of it's poor quality.
From my own experience recording adequate audio is a matter of practice, planning, preparation, persistence, and post-production.
Practice - if you're acting as your own audio talent, get some seat time and know your voice; every amateur has areas they need to improve upon and by listening carefully and objectively, you can find those. Usually enunciation, p-pops, and breathing are the challenges. Also pacing...don't be afraid to pause; and try to sound as natural as possible. I will "hear" a character in my head before I read; that way, I get the tone of the piece set, whether it's instructional, markety, or just fun.
Planning - create a script, even if you think you can wing it. If you're doing a screen recording, you may need to place your script near the screen while you "perform."
Preparation - if you are acting as your own talent and your own director, you are asking for trouble, but some people pull it off. You have to be objective with yourself and have an ear for quality--if you can't do that with yourself, you have a resource need. You also need to set up your environment to be relatively free of ambient sound. Do a bunch of sound checks and systematically eliminate any "white noise" such as air conditioners, computer fans, etc.
Persistence - take one, take two, take three...take twelve. It doesn't matter. You have to go as long as it takes to get the quality you need. I tend to record every line at least 3 times and I'll probably listen to each of those twice. Also, multiple takes probably have to be done at the same time of day. Your voice can change through the day. Coffee, lack of sleep, and of course, yelling the night before can all impact your voice. Warm water or herbal tea may sooth an errant throat if you don't have time to wait. Don't forget to leave enough of a pause for editing.
Post-Production - Adobe SoundBooth and many other products do a good job of allowing you to remove sounds, but nothing beats a clean recording! I haven't mastered Audacity for post-production filtering, but it's great as a simple tool for removing breath marks (copy in a slice of ambient sound from another part of the file onto those), and slicing and dicing.
There are full-fledged training programs that will help you become better with audio. Here are a couple resources that may speed you along your journey a little more.