I left one pawn unsupported.Other than that,does anyone have any suggestions? 

You're white, I'm fairly sure. 

You moved your knight three times, when there was no need to. He wouldn't have traded a flexible bishopfor a non-center knight, especially one that was only guarding 1 pawn, only to trade your newly centralized knight for an (now) awkwardly positioned bishop. Much better was just to continue d4, which would've won you the square, after a pawn and knight trade, and would've left you with a developed queen, open lines for both bishops, and potential attacks on Black's weakened diagonals.

 

General advice in openings:

 When a beginner, begin 1.e4 or 1.d4.

Develop knights before bishops

Castle early, castle often.

Get your rooks onto open files.

Double up your rooks on the same file.

Always be sure to keep enough power on your back rank (or guarding back rank open files) to avoid mate; nothing's more frustrating than getting checkmated when you're up a queen.

Watch out for knights and pawn pushes that can fork your pieces oddly. 

Never move a piece more than once in the opening unless it's a chance to win (significant) material or positional advantage. (I.E. win a minor piece, rook, or force him to forfiet his right to castle. 

Thanks mate.That was helpful.