Cometstarlight
What do I do now?
I was really hoping they would at least say what the research tasks are first if they are announcing Celebi. My advice is to start walking a couple Eevee and don't evolve them because it is highly likely you'll need to get an Espeon and Umbreon for the research.
Fortunately, if you walk an Eevee, you don't have to evolve it right away. You can walk it to 10k, take it off, walk another Pokemon, and put it back on when you're ready for an Espeon/Umbreon!