Almost all our themes come with the official support for WPML. WPML is a de-facto WordPress plugin which allows you to translate any part of the WordPress site. It is a paid plugin, but well worth the quality and support that comes with it.
Find the relevant part in the theme documentation which says about WPML support. Here are direct links to some of our most popular themes:
Some free plugin alternatives to WPML are:
We strive to make all our themes compatible with the free plugins above as well, but sometimes this is not possible and we do not guarantee that our themes will 100% work with the above solutions (except if advertised otherwise, of course).