VPN hotspot with setting for any VPN server preferably opensource

I've tried web search and installed one VPN hotspot app (be.mygod.vpnhotspot) from google play, but could not find in it settings for VPN server ip. The task in to connect to my OpenVPN server and provide transparent ip spoofing for devices connected to my phone by WiFi and/or USB. Is there such app (preferably opensource)? I understand root is required. Is there a way to make phone connect to some WiFi-spot and be via that app WiFi spot with VPN? If not, then get internet from WiFi and make its spot for USB tethering.