changing mesh rotation and location

how do i change the rotation and location in c++? the skeletal mesh of my char spawns somehow in wrong direction. thanks

SMeshPointer->SetRelativeRotation += 90.0f; thats what i have but obv it doest work haha how do i adress the Yaw of my rotation?

Try:
FRotator Rotation = GetSkeletalMeshComponent()->GetComponentRotation();
Rotation.Yaw += 90.0f;
GetSkeletalMeshComponent()->SetRelativeRotation(Rotation);