With this tutorial you’ll have a new blog theme ready in only three steps.In fact there are a few ways setup a new theme for your blog but we will be focusing on manual WordPress theme installation. This tutorial assumes you already have WordPress installed on your host and you are installing a “normal” theme with no advanced functionality that would require additional plugins or configuration.
Step 1: Download the theme
Download the theme. Just search for free Wordpress themes or similar phrases and look for a template that will fit your needs. Once you find a WP template that you like, preview it to see if all is ok and imagine how it shall look like on your website/blog.For this tutorial we’ll choose the Barthelme theme. Click the download link and save the .zip file to your hard drive.
Step 2: Upload the theme directory to WordPress
You need to upload the complete folder of your template to your Wordpress installation - into the following folder: yourwebsite.com/wp-content/themes.
The best way to do this is to upload the files via your Dashboard.First you need to go to Appearance->Themes and select Install Themes:
Next step is to select and install the downloaded theme from your computer.To do this you need to select Choose and after you select the theme press Install:

Step 3: Activate the theme within your WordPress admin panel
Now that the files are uploaded, you just need to activate the template. To do this simply go to your Appearance->Themes and just click Activate on the bottom of your new theme like in the image below:

Now when you refresh your website, it should load with the new Wordpress theme and if you need some customization for your theme, you are free to do some.