easiest to get going is probably https://geti2p.net/en/download/easyinstall
when you get it running allow the router to run for a while. the longer you leave it running the better connected it’ll become, it takes some time to get well connected into the network. torrenting right away is a good way to speedrun this since it’ll discover a lot of peers this way. to browse eepsites (.i2p domains, kind of like .onion) router needs to be running, and need to change proxy settings in browser.
there are guides and plugins for this but basically you want to set http proxy to 127.0.0.1 port 4444. it will proxy everything through the router. clearnet sites should go through the default outproxy (stormycloud) but i2p isn’t really build for clearnet browsing. if it’s working should be able to visit an eepsite like http://notbob.i2p (has a registry of other eepsites). things like trackers, forums, git repositories can be found on notbob.
can setup irc through it (comes preconfigured) and has built in torrent client (i2psnark). can also setup email, java router has that built in, as well as a webserver to host your own site through i2p.
if you just want to torrent biglybt comes with a router on its own, settings under “i2p helper” plugin if you just want to torrent through it without all the other stuff.
here’s an i2p magnet link to the irs chain analysis talk from last year:
magnet:?xt=urn:btih:d371d4e4cb9a3760ef79e94fde0b8edf22062e49&tr=http://tracker2.postman.i2p/announce.php&dn=chainalysis-monero-presentation-to-irs-august-2023.av1.webm
gives some insight into how they do it with their analysis tool. i’ll let you draw your own conclusions based on your own risk profile, but if you’re a target and they have enough confidence with the tool, they could grow a profile and subpoena the target exchange for kyc.