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A good place to start is this page of K+P vs K puzzles. NimzoRoy is a chess.com member and his blog has a bunch of endgame puzzles. Some are complicated studies which in my opinion aren't great at teaching thematic play but there are a lot of great problems there. Work on the single pawn endgames until you understand WHY each move is right. For example, the second problem uses the opposition to get the critical square at f7. Study the opposition and learn this stuff, then gradually build up from there. If you feel like you can evaluate any single pawn endgame correctly, you'll know when to trade into that ending and when not to. This isn't a quick fix but it should help a bit. here's the page: http://www.chess.com/blog/NimzoRoy/k--p-vs-k-endgames
Since you're a diamond member, go look at IM Danny Rensch's King and Pawn endgame series (6 videos) and his Rook endgame series (11 videos). They are fantastic, and you've already paid for access.