If you have a positive test result, it indicates that RNA from several genes in the SARS-CoV-2 (the virus that causes COVID-19) were detected, and that you were infected with the virus at the time that you produced the sample. If you have a positive test result, then you are presumed to be contagious, and if you have symptoms such as fever, coughing or shortness of breath, it is very likely that you have COVID-19.
If you are having mild symptoms, per guidance from the CDC, you should self-quarantine, meaning that you should stay home and stay as far from other people living with you as you can. If you have symptoms, you should also get in touch with your healthcare provider, so that they can monitor your symptoms and be ready to provide care if your symptoms get worse. (https://www.cdc.gov/coronavirus/2019-ncov/if-you-are-sick/steps-when-sick.html).
If you develop emergency warning signs for COVID-19, including, but not limited to, trouble breathing, persistent pain or pressure in the chest, new confusion or the inability to arouse, and/or bluish lips or face, you should seek immediate medical attention. (https://www.cdc.gov/coronavirus/2019-ncov/symptoms-testing/symptoms.html).