In order to change the language displayed within your MathWorks Account, please go to the MathWorks home page:
Please scroll to the bottom of the page. On the lower left, you should see an oval with a globe icon that shows what country the website is set to. You can click on this oval and select the country and its associated language (which is noted in parentheses). This will set the location to the selected country and the web page will display in the corresponding language.