If there is direct light on the tank, then yes, close up the blinds. If it's indirect it should be fine. I thought opening the blinds in my room would be great for the plants in the bookshelf tank on my dresser. One end of that tank got some direct sunlight, and my poor Redfish turned into an Orangefish until I remedied the sunlight problem.
Otherwise, just make sure he has a place to hide in his tank along with some leafy real or silk plants, and that you are keeping the water clean.
And it could just be that it'll take him a week or so to settle in