To buy prescription safety glasses, get an up-to-date prescription (including PD), choose impact-resistant frames (polycarbonate/TR90) with side shields, and order online or from an optical shop by inputting your Rx details, selecting lens materials (polycarbonate is best for safety), and adding coatings (anti-scratch/fog). Key steps involve verifying your prescription, picking suitable, protective frames, and customizing lenses for your needs.