Here's a quick tutorial on moving players, either from your bench or from the free agents list.

FROM THE BENCH:

Click on My Team at the top and you'll see a page like this:







If you click on the icon in the Move column next to the benched player you want to move, the icons will change to up/down arrows in a blue circle indicating which player(s) can be replaced by that player. Click and drag the benched player up to one of those positions. Then, make sure you click Submit at the bottom of the page!!








If you want to replace a player with a free agent, click on Players at the top. You'll be presented with a list of all free agents (you can show individual positions only by choosing it at the top). Click on the green + next to the player you want to add to your team.







You'll be presented with a list of your current players where you can select which player you are replacing. Click Continue at the bottom to finish the transaction (you may have to click Submit again - I didn't want to complete a trade to get the next screenshot )





Side Note: Notice, in the 3rd image in this post, the icons under Spencer Ware's name. The IR indicates that he is on Injured Reserve and the little red page icon means there is breaking news about him. You can click on his name to see current news about him -- you can click on ANY players name to see current news about that player.