Setup
When your ESP hasn't saved any wifi connections it will create a 
wifi. Connect to this wifi. Usually you get a message that you need to sign in to the network. 
Click on it and you will get to the wifi setup page. Now you can configure your wifi.
If you don't get the message to sign in to the network:
Connect to the wifi and open this URL: http://192.168.4.1/
Now you will get to the wifi setup page and you can configure your wifi.
Connect your ESP to serial monitor and set baud rate to 9600. On every boot the ESP will print its IP-Adress.
Or:
Look at your router devices list. The hostname of the ESP is something like this: ESP-RGB-Controller-8346362
The hostname is generated from the ESP chip-id. So the last number can differ.
Go into the same network as the ESP and connect to http://[IP of ESP]/
Now you can controll your RGB-Strips with your ESP board.
It's importent for some effects to set the correct number of leds. To set the number of leds click on the settings icon at the bottom right corner 
and type in the correct amount of leds in your led strip. Now click on SAVE and than on RESTART.
Now you have finished the setup and you can use your ESP-RGB-Controller. Have fun! 😄