Secure Way to Set Up Wifi Extender

I recently purchased a wifi extender and I now have to set it up.

There are three options for how to set it up:

  1. Through the app
  2. By pressing the WPS button on the router and then pressing the WPS button on the extender
  3. By connecting to the wifi network of the extender (which does not have a password) and then navigating to a webpage that doesn’t have HTTPS and enter the password for the extender.

The fact that there is no preset password is worrying. Considering that 3 is even possible I worry about what security compromises they made in implementing 1.

Is 2. the best bet here? WPS seems to have some vulnerabilities though after googling.