This is something that comes up often when answering support questions for our customers. So I have written a neat little guide to help you translate your WordPress theme using the PO file provided with your theme.
Tools you will need
The bulk of the work is carried out using a fabulous piece of software called POEdit. This software is free to use, with a premium license available to make the job even easier (aimed more at theme developers). You will also need to ensure your new language files are correctly named, so id suggest to bookmark this list for your reference (we will cover this a little more later)
The begin, head to Settings > General in your WP dashboard and use the language drop down box to change the language to your chosen region. As soon as you hit save you will notice your admin will now display in your chosen language.
Next, load up POedit and select ‘Create New Translation’
You will be asked to supply your PO file next. In most themes you will find this within the languages folder inside your theme itself. Once you have loaded the original language, you can now begin translating things how you want. Begin by choosing your new language from the dropdown box shown.
You will be presented with a long list of strings/text used by your theme – these will range from text seen only in the WP admin area to text used on the front-end (the bit viewers see) so you may wish to only translate certain areas – this is up to you. To traslate the text, simply select the line you wish to edit and place your desired translation in the box provided.
Once done, your done, you need to save both a MO and a PO file. To do this, head to File > Compile to MO… and save the new MO file within the languages folder of your theme, then head to File > Save as PO and do the same.
IMPORTANT – You must name the file correctly for this to work – to find the correct file name please refer to this list.