The Widget does not have components in the traditional blueprint sense. You will want to use a “Play Sound At Location” node, with the location being set to the character’s location. UMG is still under heavy development, so please stay tuned to updates and announcements to see the latest features.
I have an example that may help. I have used a get all actors of class (for the Ambient Sound class) and I have connected it to a for each loop. From there I set all sounds in the level to 0.0 with a “Set Volume Multiplier” node. You could pull out a reference to the specific sound that you would like to mute from the for each loop. I hope that this information helps.