Impossible. N (by Metanet Software) is a Flash / browser‑based game. The PSP's built‑in browser (NetFront) does not support Flash Player 10+ (required for N v2.0) and was never updated.
Install CFW (6.61 PRO‑C2 / Infinity) → Run N+ (PSP Minis version) from Memory Stick. Legal if you own N+.
Don't waste time on browser Flash. Get N+ or N++.