Here’s how to translate the WP Tab Widget from Mythemeshop tab labels.
1)Download and install: Poedit (for Windows or Mac), https://poedit.net/
2)Go to your plugin directory: wp-content/plugins/wp-tab-widget/languages
3)Download the default.po file.
3)Start Poedit program
4)Choose, File > New from POT/PO file, and find the default.po file that you downloaded. Make sure to choose PO from dropdown-menu in the same dialog for the file to show up.
5)Change the text strings you want to translate; i.e. change Recent, Popular and Comments strings to your language, will change the names one the Tabs.
6)Save the file as: mts_wpt-pt_BR.mo and mts_wpt-pt_BR.po
7)Upload the files to your server:
https://www.yourserver.com/wordpress/wp-content/plugins/wp-tab-widget/languages
Thats it. Hope that helps you out.