Parameters that can be animated will display a red animation indicator next to them while Animate mode is on. Simply type a new value or use the Explore feature to change the parameter.
A blue dot next to a parameter means that it is animated (i.e. has one or more animation keys). If the blue dot turns into a yellow marker, this means that the parameter contains an animation key at the current frame. In this case, editing the parameter while Animate mode is on will change the value of the key at the current frame instead of inserting a new key.
If Animate mode is off, editing an animated parameter will adjust the values of all its animation keys. For example, if a parameter animates from the value 1 at frame 1 to 4 at frame 100, and the current frame is 1 and you change the value to 2, the value at frame 100 will change to 5. Floating-point parameters with exponential interpolation, such as Magnification and Color Density, are scaled instead of translated.
Complex, floating-point, and integer parameters will be interpolated smoothly between animation keys. You can also animate enumerated and boolean parameters, but they will not be interpolated.
Right-click a parameter for a menu with options to insert a new key at the current frame or to remove the existing key, and to jump to the previous and next key for that parameter. See Editing animations.
Inserting a key manually is useful if you want to animate a parameter from frame 20 to frame 30, for example. If you just move the time slider to frame 30 and change the parameter, the parameter will be animated from frame 1 to frame 30, which is not what you want.
Instead, first move the time slider to frame 20 and insert a key there (which does not change the value of the parameter). Then move to frame 30, turn Animate mode on, and edit the parameter to animate it.
Next: Animating gradients