In generations 4-7, you can only evolve Eevee into Leafeon and Glaceon if it levels up near the Mossy Rock or Ice Rock, respectively. It needs to be a level-up to trigger the evolution.
As of generation 8 onwards, Pokemon that are level 100 can evolve if the right conditions are met if a Rare Candy is used on the Pokemon. The Pokemon will not level up, but it can trigger the evolution.
Additionally, in generation 8 onwards, you can evolve a level 100 Eevee into Leafeon/Glaceon by using a Leaf/Ice stone.
Tl;dr, you cannot evolve a level 100 Eevee into Leafeon/Glaceon in generations 4-7. You would need to breed/catch a new Eevee, or transfer up to modern games.