Welcome to the forum. I'm sure you will find this a very helpful place to ask questions and learn Vegas Pro.

I'm not sure if I understand fully, so apologies if the following is not what you are after.

Applying effects can be done at either event level or can be applied to the whole track. In Vegas there are often multiple ways of achieving the same thing.

To apply a video effect to a single event (clip), simply click on the small icon in the extrme bottom RH corner of the individual event, it is a little white vertical rectangle with a small dot on either side. That will bring up your effects menu, click on the effect you want and then adjust the parameters for that effect. It will be applied to that event and you can see the effect in your preview window on screen. To apply the effect to the entire track, you click the similar icon in the track header (over on the extreme LH side of the track), works the same way.

I'd suggest you start by downloading the PDF manual for Vegas Pro from the Sonycreative software website as this is an extrmely useful reference, particularly when just learning. Additionally, if you simple Google "Sony Vegas applying video FX" you will find lots of helpful information and / or videos on Youtube / Vimeo.

Finally, I don't ever denoise video, so I'm no expert, but if you search this forum you can find reference to "Neat video", which seems to be the preferred option for many requiring to denoise video.

Hop that helps.

Duncan