I don't have Familiar button ....
How Can I Get It⁉️
From the screenshot it looks like You are just starting out once you unlock familiars that have active skills the Icon will appear it wont show until then
Seems like you are new to game welcome and have fun
If you have familiar with active skills and still there is no button it might be a bug [seems highly unlikely] report it to live support they will sort it out for ya