A handwritten look usually means buying somebody else’s handwriting. This makes yours into a font instead, and a real one: an actual font family your site installs and every part of the editor can use.
There are two ways in. Draw the letters here with a mouse, pen or tablet on a proper type grid, with baseline, x-height, cap height, ascender and descender drawn while you work and the neighbouring letters faint beside them so the shapes line up from the start. Or print the ruled sheet, fill it in with your favorite pen, photograph it, and let the registration marks straighten the page and read every cell in order, so nothing has to be matched up by hand.
Because the drawing itself is kept rather than a picture of it, one alphabet yields a whole family: Light, Regular and Bold as genuine weights, plus an italic by slant. Accented characters are composed for you, so drawing the plain letters and the accents once covers German, Spanish, French, Portuguese and Italian. Cursive mode puts entry and exit marks at a fixed height and closes the gaps so the letters visibly join. Spacing comes from the real ink of each glyph, with a tracking slider and a per-letter nudge on top.
One click installs the finished font into this site’s font library, where it turns up in the font picker, brand kits, templates, curved text, text on a path, WordArt and every layer style, with no reload. The font file doubles as the project file: open it again later and every stroke is still editable. It is all computed in your browser and stored on your own server.