Something like this should do it.
// After you set the animation on your sprite:
sf::IntRect rectAnimFrame = sprite.getTextureRect();
// to draw sprite from bottom right:
sprite.setOrigin(sf::Vector2f(rectAnimFrame.width, rectAnimFrame.height));
// to draw sprite from bottom center:
sprite.setOrigin(sf::Vector2f(rectAnimFrame.width / 2.f, rectAnimFrame.height));