1. Here is a useful introduction series to the Lumia 521 which you may want to study.
Nokia Lumia 521 - Support, Updates, Downloads and User Guides, Troubleshooting - Nokia - USA
2. I find that the small screen is easier to operate with a stylus. If you have small fingers, the finger touch is OK - it works well. But sometimes the links are really tiny and a stylus is handy. You should be able to get one from your nearest brick and mortar store. I paid $7 and change for mine.
3. I don't know whether you saw my suggestion regarding the MicroSD card. I have a 32GB model (class 10) but if you have less music, videos, etc., a smaller one may also do. The phone does not have a lot of storage that's why the SD card is handy. Once you are halfway setup, you are left with appr. 3.5GBs of phone storage and that I want to keep for future apps. With the SD card you can direct e.g. photos or videos that you take with the camera to the SD card - so that is saving me internal storage space. Plus I have a ton of stuff I copied from my desktop. There are a few caveats regarding filetypes that we have to discuss later.
4. Preferred music filetype is MP3 but WMA works too but with a different player.
5. For videos WMV but if you convert beforehand, use the Freemake converter. The Format Factory played quite an act on me and the bitrate was all wrong and did not play on the phone - although it played on the desktop.
6. If you have PowerPoint shows (I have a lot), make sure the embedded sound is in WAV. If you outsmart yourself like me and use MP3s with WAV headers, PP 365 refuses to play the sound.
If you have radio and TV stations you like to watch, make a docx file with the URLs and put it into a folder on the SD card. That works well for me.
7. Make sure your SD card folders are not called Music, Videos, etc. because the phone will create it's own set with those names. I called them sdMusic, sdVideos, etc.