I put a gradient fill on an empty layer to get a background, but now I want to tweak it a bit. The problem is I'm not sure where to go to edit the effects I put on a layer. How would I go about this?
Are you talking about Photoshop (Creative Cloud)?
It's not clear from your OP.
Layers Palette. Top pull-down Window (far right) > Layers.
See below.
Click on the fx at the bottom of the palette.
I wanted to edit an already existing gradient though, not make a new one
What do you mean by edit?
There are so many things you could do to an existing gradient.
What are you trying to achieve?
I'm trying to change the colors and/or opacity a bit. I don't need help with editing so much, I just can't find where I would go to edit the gradient
Opacity is adjusted in the Layers palette, towards the top. Look for the word "Opacity:" and a little box to the right of that word where you can change the percentage from zero to 100.
Changing the color is a bit trickier ... partly because your request is still too vague to really understand what you're trying to do.
My favorite technique is to have the gradient exist in the Mask and a solid color the Layer. (see below)
Then you're not changing the gradient, and you can change the color at will.
This is what I've got, if it helps. What is unclear, exactly?
I don't see any gradient ... either in the Layer or the Mask.
It's pretty hard to adjust something that isn't there.
Rest assured, it's there. Its transparent and very light which is why you weren't able to see it