I dl the linked repo (so the whole HA fork by Imick) by clicking the Green Code button (select zip) and selected the Overkiz component in that. Copy that as complete folder into your custom_components folder. Then add a “version” key in the manifest file and restart HA.
{
"domain": "overkiz",
"name": "Overkiz (by Somfy)",
"version": "0.0.1",
"config_flow": true,
etc etc
It will show your newly added integrations in the discovery.
Now, first allow the developers api in your Somfy device, by logging in at Somfy on your device and click allow.
then configure the integration using the config flow, and be sure to scroll down all the way to:
(I did not do that correctly above, so that is still a cloud install You can see it in the Connected to: field., where it should list your local device id key )
Next screen wil bring you to your credentials I which your enter your own key replacing the xxx’s, user and pw.
and you’re set