Note that each of the few characters that the font has on it correspond to an unicode emoji itself. It is not like fontawesome, you can type emotes on your phone and if it is one of the ones contained in the font then the one in the font will be used.
I did, but I did not thought it was useful for me at first sight. I will read it carefully. Meanwhile, how can I know the emojis value in which I have to set each SVG ?
Then look for that code in the list in Window > Glyph Info. There you can make a new glyph with that name/unicode combination. Or, if you have the glyph already, assign a “uni” name (uniXXXX for for digit codes and uXXXXX for five digits) to the glyph and Glyphs will automatically find the right name.
Or you just type/insert the emojis yourself in a text editor or something (or even in the Glyph > Add Glyphs dialog field), then select them and run the Unicodes to Glyph Names service, then you have the proper glyph names to paste in the Add Glyphs dialog (or to press Generate if you are already there). Read more about Services.