Not trying to be a jerk by pointing this out, but a lot of times questions like the OP's can be answered....by simply reading the patch notes

The following quote is taken from the page below

http://na.finalfantasyxiv.com/lodest...c82c85a550f9a0

Players can join a party in progress by first checking the "Join Party in Progress" box in the Duty Finder menu, then speaking with the Wood Wailer expeditionary.