First, find and download a theme. Then go to your administrative back-end and click Appearance on the left menu. Now click Install Themes at the top tab. Click Upload below the top tabs. Click browse and find the theme you downloaded. Click Install Now. Now Activate the theme. It should have prompted you when it finished installing. If it didn't, do this: Click Manage Themes tab at the top. (if it isn't there, click Appearance on the left menu first). Scroll down to the themes and click the Activate link at the bottom of the description of the theme. Viola!
Or simpley... upload the themes folder (not .ZIP) to the wp-content > themes folder , go into your back end and activate it
First you can open WordPress. After choose theme option. now choose your theme in to your p.c. and upload them. after upload you can active it. Now your theme will be change.... I think it is helpful to you
Starting at your dashboard, path is: Dashboard >> Appearance >> Themes >> Search >> Select >> Install >> Activate.