I am using the official google material icons: https://material.io/icons/
I want add some icons created by me, in svg.
how can I do it?
You will need to create your own web font.
If you've already got SVGs then you can possibly use something like https://icomoon.io/app/ to create one. I've not used it so can't help any further with that.
If not, you'll need to find a font authoring tool that exports to woff or woff2 or whatever web font format you need. (I think the material one is woff2)