It's really simple, go into the toolset and make a new module with a blank area (it's pretty much self-explanatory). Then open up the area and go to where it says Wizards on the toolbar and bring up the Item Wizard. Select the type of weapon you are using then hit next and name it whatever your heart desires. The next screen that comes up will put it in the right slot for use later (should you choose to do so), select the right type of weapon from the drop down lists then hit next. In the next screen check the box that says 'Launch Item Properties.' When the item properties comes up go to the properties tab and scroll down the drop down list on the left with all the different properties until you get to visual effect. Double click on the visual effect you want to see and it will show up in the preview picture to the left. When you want to remove a previous visual effect, click on it in the Assigned Properties box and hit the arrow pointing to the left and it will remove the visual effect to allow you to look at a different one.
I hope this was easy to understand. If you have questions find me on AIM.