You do not type it from a keyboard; you copy it. Press the copy button above and paste it into any app. That is the whole point of Unicode styled letters.
Where can I use the Squared J?
Anywhere text is accepted: Instagram bios, TikTok names, Discord, WhatsApp, gaming profiles and documents. The full Squared alphabet is linked above.
What is the Squared letter J?
It is the letter J rendered as the Unicode character 🄹 (code point U+1F139), part of the Squared styled alphabet. It is a single character you can copy and paste anywhere.