Welcome to SA! Most likely if the giveaway doesn't start til the 4th then they wont accept entries until then. If you can go directly to the sweeps site for the giveaway and access their rules, it probably says this. You may just have to wait until the 4th to start entering that one. Once the sweep is listed here at SA, you can add it to your "my sweeps" category and enter it through here everyday or however often the rules say you can enter. I hope this answered your question. Do you mind me asking what sweep it is? opcorn:
As spoon03331 said, if the giveway doesn't begin until 8/4, then you can't enter until 8/4.
If you are asking how to use this site to enter a sweepstakes, it would be a good idea for you to watch this video and read many of the questions and answers here in the Newbie forum.