Go to www.computeraudiophile.com and post your questions there. That forum is all about computer audio and you'll get lots of helpful advice(not that there aren't other helpful people like billybob_jcv here at head-fi). The CA website also has tutorials for things like ripping from CD's and ripping from blu rays(I would suggest avoiding blu rays until you're more adept, however). It would also help if you could be more specific regarding what you would like to do. There are CD ripping programs, media players, streaming services, high resolution audio download sites, etc. My last bit of advice would be to avoid mp3 if at all possible and go for "lossless" files instead(FLAC, ALAC, WAV, AIFF) for better sound quality. There are also DSD files but I don't know if your DAC plays DSD and, anyway, I'm getting ahead of myself here.
As billybob_jcv points out, the possibilities are virtually endless. I would start with CD ripping software(I use dbpoweramp, but exactaudiocopy is also well regarded). You should rip your CD's in uncompressed form and in CD quality(16/44.1, otherwise known as "redbook"). If you want to dive right into downloads, Bowers and Wilkins Society of Sound is a good place to begin seeking out downloads at CD quality or better. Some musicians also sell CD quality downloads on their official web sites.There are lots of other download sites out there but I would strongly caution staying away from bit torrent sites that traffic in illegal downloads.
You can take a peek at www.hdtracks.com and www.acousticsounds.com to get a flavor of what awaits for you in the world of high resolution downloads. Tidal is a highly regarded streaming service by subscription and it's available in Europe. For now, however, I would suggest starting out with your own CD rips and then venture out into these other areas, if you wish, some time down the road.
I use jriver media center as a media player as it does audio AND video, plus it has a lot of nice features that I've yet to outgrow (and they provide lots of support for users). Of course, there's other media software out there that would be equally valid choices(iTunes and Windows Media Player have their limitations, as does everything, but they are available for FREE).
I think I've given you enough to get started. Enjoy the musical journey!