For many, using BitTorrent (or any client) is complicated, since it is not one of the types of programs that you put a word to search for and download files.
BitTorrent is a system that is based on small files in format .torrent, more commonly called torrents, in which certain information which then serve so that the client program in which we are going to download the files, knows what it is that it has to download and from where.
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There are various torrent sites such as Mininova, IsoHunt, Meganova, etc. On these sites we can search for the file we want to download, download the torrent, and then open it with any BitTorrent client.
For example, we want to download an Ubuntu ISO (totally legal), we go to IsoHunt, we search with the term ubuntu, a series of results appear, we choose the one that seeders (I explain its meaning later) have, we downloaded it to our PC.
Now we open the BitTorent client that we choose, in this case uTorrent, we are going to File -> add torrent, we search among the directories for the torrent that we had previously downloaded and click on Open. Now the file starts to download.
Seeders: seeders are the users who have the same file that you are downloading, but complete, that is, they have already finished downloading it and are uploading it for you.
Leechers: These are the ones that still have an incomplete file, but are still sharing it.
This procedure is basically for use with any client, search for the torrent on any torrent site, open it with the chosen client, and download!