Frequently people post asking how to see the games because they don't have MLB Network or cable or are in a new town or something.
Short version first:
For video, outside the US and Canada, you can stream online at postseason.tv. $5 covers the whole postseason.
For video inside the US and Canada, rights are held nationally by TBS, MLBN and FOX, you will have to watch at home, friend's place or a sports bar. If a game is on TBS you may be able to stream it at http://www.tbs.com/watchtbs if your cable/satellite company participates.
For audio, anywhere in the world, you can listen using an existing mlb.tv, Gameday Audio subscription or get a new postseason.tv subscription for $5. You can listen on your mobile device using your existing or new At Bat app purchase.
For all postseason games, video rights go to national coverage outlets. For the first round, most games are on TBS with two of them on MLB Network. In the second round, all NLCS games are on TBS, all ALCS games are on FOX. The World Series is on FOX.
So option 1 is to find the network that is carrying the game and watch it there. No US local outlet (like CSNCA) will get the games.
If you cannot watch it there, your next hope would be typically to stream it. Network video rights override streaming, so if you are in the US or Canada you cannot stream the games online unless you have a way to stream MLBN, TBS or FOX. TBS games can be streamed at http://www.tbs.com/watchtbs if your cable/satellite provider participates. A mlb.tv subscription will not allow you to watch the games live inside or outside the US but you can watch them as replays 90 minutes after the game ends.
A postseason.tv subscription will allow you to watch companion coverage, which are multiple fixed camera angles which really aren't very good. If you are outside the US & Canada it will allow you to watch the main feed too. So postseason.tv is very viable outside the US and Canada. You cannot watch replays with postseason.tv in the US, not sure about outside the US.
What if you just want to listen to the game? First line is again the As radio network. If you get KGMZ or a local affiliate, you can listen to the game there. The streaming sites for radio stations will not work, they are forbidden from streaming the game on their sites.
You can however use Gameday Audio to listen to the game. Gameday audio can be purchased separately, and it is also provided with a mlb.tv or postseason.tv subscription. You can also use the MLB At Bat app on your portable device (iOS, Android, Windows Phone, etc.). So if you want to listen to the game online, you can either use your existing subscription or you can buy postseason.tv (it is cheaper than gameday audio or mlb.tv) and listen to it online.
If you are in the US & Canada you cannot video stream the game live from any service, you must watch it on the network that carries it (TBS or FOX). You can video stream the game outside the US and Canada on postseason.tv or get low-quality companion coverage (with radio audio) from postseason.tv either inside our outside the US and Canada.
You can audio stream the games from mlb.com using a mlb.tv, Gameday audio or postseason.tv subscription anywhere in the world. You cannot audio stream over radio station' online feeds on their webpages.
Let's go As!