I am no expert on anemones, but it looks okay. From what I hear anemone's can be finicky, they need pretty stable conditions. He's already in your tank so the best thing you can do would be to stock your tank quite gradually. And feed the anemone every couple days. I hear some feed their anemone every day. If the anemone spits the food out, try giving it a smaller piece. Occassionally it will shrink up and look like its dying... its just expelling waste. If its shrivelled up and its mouth is drooping open, at that point it may be on its deathbed or severly unimpressed by the water quality. Just keep an eye on your conditions and feed it regularly is my best advice.
My anemone sometimes wanders around and gets in a spot where I can't feed him, so I wait till he moves to a more appropriate spot then he gets his silversides again.
