Follow instructions for the client setup and then add the following to your hosts file at C:\Windows\system32\drivers\etc\hosts.

      5.161.57.140 erupe.custom
      5.161.57.140 mhfg.capcom.com.tw
      5.161.57.140 mhf-n.capcom.com.tw
      5.161.57.140 cog-members.mhf-z.jp
      5.161.57.140 www.capcom-onlinegames.jp
      5.161.57.140 srv-mhf.capcom-networks.jp

Choose any username and password when you first sign in using the launcher, that will be stored as your account on the server for future logins.

Choose "custom server" at the bottom of the drop-down, that will use erupe.custom.