First go to your word press admin and click add new themes in appearance options. Now click on upload and then click browse. Now you have to locate your theme in .zip format and then click install now. If you have successfully uploaded that then you will get a message "theme installed successfully". Now you can click on preview to preview your theme, if you think it's fine then you can click on activate to activate your theme. If you want to change the font color, layout etc. then click on design option under the thesis options and make your changes there. Now you can go to your site to see the changes.