Once the mod is installed, follow the steps below.

1º Open Vpet
2º Right click on it to open the interactions menu.
3º System / Settings
4º A new window called "Settings" will open, the last tab is the one that is focused on mods
5º When you reach the last tab, the subscribed mods will appear, enable the EdgeTTS mod
6º Restart Vpet
7º Right click on the Vpet again
8º Now when you put the cursor over the system the Mods option will appear, move there and select the EdgeTTS mod
9º When clicking on EdgeTTS, a new window will open with the language options where we can choose what we prefer
10º Save changes and enjoy your virtual pet.

Note: I have had problems when closing and restarting the application because it does not correctly save the language voice that I like, putting a US by default.

If someone knows how to set the language that we like by default, you can explain it here to help the rest of the community.