Create a Devanagari Glyph

How can I start to create a devanagari script glyph? I’m able to see just latin script.

Add the Devanagari character set from the Insert Character dialog. Double-click the first in the range, then Shift+Double-click the last to add them all.

Then starting drawing your glyphs in the Glyph Edit Window for each added character that you want.
Insert Devanagari Characters.png

Thank you Bhikkhu brother!
could you guide me please how to add some extra glyphs (I think those would be without unicode code-points) for ligatures, because devanagari script has so many ligatures.
Thanks in advance!

I have no experience of making Devanagari fonts. Take a close look at an existing font to see how the ligatures are drawn and see the OpenType editor to see how glyph substitutions are used to display ligature glyphs that have no code-points.

Thanks!