If every player listed says they are fully scouted, that means you haven't sent your scouts to discover more players yet. The game starts you off with like 25 fully scouted "blue chip" prospects but after that you need to send your scouts to discover more. Click X on a highlighted scout and choose the region, position and attributes you want. The players they discover will only be 20-25% scouted to start off with.
To then fully scout those players, in the scouting menu, highlight the scout you want to use, click L3 to toggle down to the prospect list, click X to scout that player.
The way I've always done it is discover players all of April, and then scout as many as you can fully for May and the first few days of June before the draft. But it always leaves me wanting more time.