For my Bloodrager class I gain effects when i rage, such as haste/blur/displacement. When I look into "Edit Mods" all it gives me is numbers of stats to change. How do I apply effects such as haste to myself? Use the "Custom Macro to Run" item at the top maybe?
In general you are correct. An Active-Mod is a modification you can apply to your token that changes character values (primarily). So you can tweak character stats, saves, attacks, resistances, movement, vision, global skills. For some of the more off-beat tweaks (like BAB, number of attacks, size change) I have used macros to achieve some success.
There is a Haste active mod you can look at as an example (or if it is exactly what you need, just activate it as needed). As Elorebaen mentioned, a macro placed on your token to toggle a specific mod might make your game play faster and easier. There is a sample macro in the Sample category of the Campaign macros. For example, I had a pixie-rogue that was continuously toggling Invisibility. If you use the main Active Mods macro, it is slow as it brings up the full list of mods and then you choose which you want to activate/deactivate. With a custom toggle macro on the token, it will quickly toggle the hard-coded mod for you. Also remember the character sheet will allow you to easily disable an active active-mod.