Operator overloading on class templates

I'm having some problems defining some operator overloads for template classes. Let's take this hypothetical class for example.

template <class T>
class MyClass {
  // ...
};

• operator+=

  // In MyClass.h
  MyClass<T>& operator+=(const MyClass<T>& classObj);
  
  
  // In MyClass.cpp
  template <class T>
  MyClass<T>& MyClass<T>::operator+=(const MyClass<T>& classObj) {
    // ...
    return *this;
  }
  

  Results in this compiler error:

  no match for 'operator+=' in 'classObj2 += classObj1'
  

• operator<<

  // In MyClass.h
  friend std::ostream& operator<<(std::ostream& out, const MyClass<T>& classObj);
  
  
  // In MyClass.cpp
  template <class T>
  std::ostream& operator<<(std::ostream& out, const MyClass<T>& classObj) {
      // ...
      return out;
  }
  

  Results in this compiler warning:

  friend declaration 'std::ostream& operator<<(std::ostream&, const MyClass<T>&)' declares a non-template function
  

What am I doing wrong here?