Without knowing exactly what type of file it is, you may have to play around. Hopefully, you won't do too much damage.
Rather than going into Filezilla or putty, I would suggest going into echanneliser. Make sure you update echanneliser to the most recent version. Connect the box to that using the box's IP address. Then, once your box has been read, create a new bouquet. Give your new bouquet a name and then open it. You will find it empty. Right click where a box will appear. Then click onto "import m3u". If it is a URL, click onto the third and final option (I think it says 'Link' or something). Then copy and paste your URL over. Hopefully the channels will then appear on your new bouquet.
If it isn't a URL, hopefully it is a m3u where you follow the same instructions using echanneliser but when you right click your empty bouquet, go for the second option from "import m3u" (I think off the top of my head). Copy and paste the m3u (from Notepad) where hopefully the channels will transfer over to the new bouquet.
Sent from my SM-G925I using Tapatalk