Point your web browser to http://127.0.0.1:8123 to use the node.
Create a new directory (with the button labelled "create a directory"). Your web browser will load the new directory. Now if you want to be able to come back to this directory later, you have to bookmark it, or otherwise save the URL of it. If you lose URL to this directory, then you can never again come back to this directory.
You can do more or less everything you want to do with a decentralized filesystem through the WUI.
P.S. "WUI" is pronounced "wooey".
Prefer the command-line? Run tahoe --help (the same command-line tool that is used to start and stop nodes serves to navigate and use the decentralized filesystem). To make commands like tahoe ls work without the --dir-cap= option, you have to put a directory capability (e.g. http://127.0.0.1:8123/uri/URI:DIR2:yar9nnzsho6czczieeesc65sry:upp1pmypwxits3w9izkszgo1zbdnsyk3nm6h7e19s7os7s6yhh9y) into ~/.tahoe/private/root_dir.cap.
As with the WUI (and with all current interfaces to Tahoe), you are responsible for remembering directory capabilities yourself. If you create a new directory and lose the capability to it, then you cannot access that directory ever again.
P.S. "CLI" is pronounced "clee".
You can plug Tahoe into your computer's local filesystem using the FUSE extension, found in the contrib directory. Warning: unlike most of Tahoe, and unlike the rest of the user interfaces described on this page, the FUSE plugin doesn't have extensive unit tests that are automatically run on every check-in of the source. Therefore, we don't for sure how complete and reliable it is.
P.S. "FUSE" rhymes with "booze".
Want to program your Tahoe node to do your bidding? Easy! See webapi.txt.
P.S. "WAPI" is pronounced "wappy".
You can chat with other users of and hackers of this software at http://allmydata.org.