Running WordPress in Arabic (RTL)
Arabic dashboard, right-to-left layout and bilingual sites.
Arabic site and dashboard
Go to Settings → General → Site Language, choose العربية and save. WordPress switches to right-to-left automatically, as long as your theme supports RTL. Most modern themes do; check the theme's description before choosing.
Each user's own language
Each user can pick their dashboard language under Users → Profile → Language, so you can run an Arabic site with an English dashboard, or the reverse.
Arabic and English on one site
Use a multilingual plugin such as Polylang or WPML. Each page gets a translation, and visitors switch languages with a menu.
Choose Arabic web fonts that are designed for screens, such as those on Google Fonts, for readable text.