First problem - you execute the if(name is address_book... statement every time you read a name when building the address book. De-indent that whole block to fix, but read further (you won't de-indent if you follow the below).
After that you have properly built the address book, but you are not input'ing the names to look up. You need to do that somewhere between lines 6 and 8. Putting a while True: at line 7, not indented, followed by name=input() will start the cycle to get names to look up.
Right after you read the name, you need to check if it is empty ("") and break out of your loop if it is.
In the next if statement you mean in, not is. (current line 8)
phone_number is meaningless at this point. You want to look up the number in that address book you worked so hard for. So, your print statement should be similar to
print(name+" = "+address_book[name])
Almost there...