Hello, I want to upload some hotlaps in LFS world, but I really don't know how I can view spr files under Windows. Could you help me, please ?

Go to hotlap charts, then on the right side you can find that option to upload the spr. You can download hotlaps by clicking on the laptimes.
Paste the spr files into your LFS/data/spr folder. Then open LFS - replays, here you go!

OK, thank you very much, I can upload my hotlaps now !

Good.