How do you define a snippet on a visual selection?

[ThSGM]

This snippet is supposed to apply to visually selected text. However, I don't know how it is activated. Can you explain?

  "prefix": ["\\eqlabel"],
  "body": [
    // Automatically generate a label from the contents of the equation, deleting any backslashes or ambersands.
    "\\label{eq:${TM_SELECTED_TEXT/[\\\\&,]//g}${1/[\\\\&,]//g}$1}",
    "$TM_SELECTED_TEXT$0"
  ],
  "description": "Create an equation label that is automatically generated from the selected text."
},`

In classsical neovim or Ultisnips, you can essentially select text, then hit tab, then enter your snippet. Upon escaping, it applies the snippet.

However, I just don't understand how it can be activated in the vim mode.