That is not a lot of information. What kind of computer do you have? Windows, Mac or linux?
What did you download?
It's okay. Delete whatever you downloaded. Download the public build again, then in your downloads folder -> Right click the file and look for 'extract' or 'zip' or '7zip' or something like that. Then find 'extract here...' or where ever you want it, then in the extracted file look for Tamer.exe (the one with the picture), click that and you should be playing