First go to http://www.google.com/webfonts and select a font. Then from the instruction of Google Font usage, you should see something like this: <link href='http://fonts.googleapis.com/css?family=Raleway:200' rel='stylesheet' type='text/css'>
Next, copy the red hightlighted text and go to Theme Customizer > section "Styles" > Google Font Family, paste the hightlighted text into this box.
To use the specified Google Font, apply the class googlefont to any heading, span or div in your content. Some examples:
Google Font example 2
To change your website logo, go to Theme Customizer > section "Header" and upload your logo.
To adjust the top margin of logo, define your custom CSS, for example: .theme-logo { margin-top: 10px; }
The logo height will be changed according to the header size used in Theme Customizer.
To translate the theme, you may use a popular translation software Poedit. It is a free software available in Mac, Windows and Linux. You can download and install it then follow below to translate your theme.
Start Poedit and go to File > Create new catalog...
In the Project Info tab, set the project name and version. Select your target language in the Language dropdown and ignore the other options.
Click on the Paths tab, then click the New Item icon. This will create a new entry in the list below. Enter double dots ".." like below.

Go to the Keywords tab, for each of the following strings, click on New Item and type the characters indicated:
__
_e
_x

Click OK and save it in the languages sub-folder in your theme folder. Name the file that match your language locale. For example, if you're translating into French, name it fr_FR (read this list for other codes).
Poedit will scan all strings available for translation. When it's done, you'll need to go through the list and enter the translation text in the lower box. After you finish translating the strings, click File > Save and Poedit will generate a .mo file (eg. fr_FR.mo) automatically when save. If you don't see the .mo file, go to Poedit > Preferences, under the "Editor" tab, check off "Automatically compile .mo file on save".
Upload the generated .po and .mo files to the "theme/languages" folder on your WordPress site through FTP. One last step is to open the wp-config.php file in your WordPress directory. Look for the "WPLANG" setting and add the language code. For example: define('WPLANG', 'fr_FR');
To create your own CSS styles or override existing CSS styles, you can use one of the following methods:
Child themes make customizing your theme easy. Many times, you want to edit the theme's php files but forgot what you edited and what needs to changed in the new theme. Child themes can help you solve this problem. A WordPress Child theme derive its functionality from the parent theme, and then override the styles and functionality you want to modify without directly changing the parent theme.
Creating a Child Theme:
/*
Theme Name: parenttheme Child
Description: Child theme for the parenttheme theme
Author: Your name here
Template: parenttheme
*/
@import url("../parenttheme/style.css");