vROps is a web application, so the only way to change your vROps language is to change your browser language.

Firefox

You need to go to your preferences, then content and choose your preferred language to display. You need to put your preferred language on the top of the list.

Refresh your tab with vROps open.

Chrome / Chromium

On the Settings page, go on the advanced settings and under Languages, click on "Language and input settings", add your preferred language and drag it on the top.

Refresh your tab with vROps open.