Assorted Frogs X Fresh Animations works with either an OptiFine setup or an EMF and ETF (Entity Model Features and Entity Texture Features) setup. A plain unmodded client won't show the custom models or animations, so make sure one of these setups is installed first.
Turn the pack on
1. From the title screen or the pause menu, open Options > Resource Packs.
2. Find Assorted Frogs X Fresh Animations in the Available list and click the arrow to move it to Selected.
3. If you run other packs that change mobs or animals, put this pack above them. Packs higher in the list override the ones below.
4.
Check that it worked
1. Load a world and travel to a swamp, the easiest place to find frogs.
2. Look for several frogs at once. With the pack working, you should see a range of colours and patterns instead of only the standard vanilla frogs.
3. Watch them for a moment. They should hop, blink and move smoothly with the Fresh Animations motion.
If frogs look vanilla: go back to the Resource Packs screen. Confirm the pack is selected and that no other mob pack sits above it.
If frogs have custom skins but stiff or missing animation: your model-loading setup isn't active. Make sure OptiFine is installed, or that both EMF and ETF are present, rather than only one of the two. Then reload the pack.