A home pregnancy test measures the amount of HCG hormone that is in your body. It takes a while once you have conceived for your body to build up enough to show up on a test.
It is best to wait until you have missed your period to take a HPT. However, most websites will tell you that once you have conceived and the egg has implanted you can test, as this is when your body starts to release the hcg hormone.
In the short, if you know when you ovulated you can test anywhere between 8 dpo and your period. If you test before your expected period, you could get a false negative, so if it comes time for your period and it is late, test again.
I had implantation bleeding on Sunday and took a test that night. It was 10 days past ovulation (dpo) and have a positive pregnancy test!