Pamela E Jones
What computer operating system is involved with your Premiere Elements 14?
Are you looking to lighten spots within a single frame or to vary the lighting across the duration of the clip?
If the latter, have you gotten involved in applying brightness effect or other lighting darkening effect and then keyframe that property so that the effect varies across the duration of the clip rather than being applied uniformly to the whole clip?
What tutorial have you been following?
Please give more details.
Keyframes for a given property can be set under Adjust Tab/Adjustment Palette/ and Applied Effects Tab/Applied Effects Palette as well as at the Timeline level (clips' "rubberband").
More on that next.