Can I say, first and foremost, please use a dynamic piece purchased from one of the excellent vendors who really do dynamic clothing properly. Mesh Density and Design really affect a successful simulation, and when you are trying to learn something, it's important to eliminate potential problems that you can probably avoid or fix when you have some experience, with a well designed product.

Second, with the advent of Poser 11 it's necessary to set up your simulation and then SAVE the file before running the sim. Most instructions you find in tutorials will not mention this as it only became an necessity with P11..

Here's a cloth room tutorial to get you started: https://www.renderosity.com/mod/tutorial_premium/?page=info&tutorial=11