In order to get help or help your brotherhood, you should click on the "House of Brotherhood" or open chat (by tap on the arrow on the right side of the screen).
After tapping on the House of Brotherhood, you will see the following window:
Here you can request assistance through the "Request troops" or check what brotherhood troops you already have by tapping on the "Brotherhood army".
When you click on "request troop" you will have a dialog window in which you can write a message (such as a particular type of troops, you would like to receive), or leave a default message.
To check the status of your request, tap the arrow on the right side of the screen to open chat window.
In the chat you will be able to help the members of the brotherhood, by tapping on request or renew your request and make it last one in chat feed (it can be done in 15 minutes after request. You can also skip this timer by taping "skip for 2 rubies" button).
It is important to note that at one time the player can refill a maximum of half of the capacity of House of the Brotherhood. After renew, it is possible to donate more troops (so full of "House of the Brotherhood" can be obitained even from one player for two requests.)
The number of troops that you can donate to the brotherhood depends on your level of "House of the Brotherhood" and is equal to 10 units per level.
To use the donated troops in battle, choose a flag with the emblem of the brotherhood in the units bar: