The main way in which we are called to love the church is in love towards the members of the particular congregation to which we belong. (This is obviously to take for granted the very first act of love towards the church, which is to join yourself to a particular congregation!) That means practical care, and spiritual care - not one without the other! And spiritual care includes the duty to pray for one another, to encourage one another, and, yes, to rebuke one another where necessary. All of this is part of love. We are called to love each member of the church, not because they are lovely, but for the sake of the Lord Jesus, to whom they are united just as we are by faith and the Holy Spirit. That includes the awkward ones, the ones who wind you up something chronic, and the ones from whom you can expect little return. That is the calling.
Although this is the front line of love, the place where our love for the church is most tested, I want to suggest that it is not the whole of the duty. We are to love the members of the church, but the church is more than a group of individuals. The church is a body, the body of Christ; and that body is manifest both in individual congregations and in the whole of the church throughout space and time.
To love the church as body is to love the church in the things that it does corporately - to love worship, to love the preaching of the word, to love the sacraments, yes, even to love business meetings. And in the same way that loving an individual does not mean popping into their life when you feel like it, to love the body of the church means to be committed to coming together, not to give up meeting together. And in the same way that loving an individual does not mean just loving the things about them that you find lovely, to love the body of the church means to participate in those activities that you personally find less attractive, to sing the songs you don't like, to turn up to the prayer meetings that you really struggle with.
And to love the body as it is catholic, that is to say, as it extends throughout time and space, is to love the church in all its messy history and all its messy present. Not, of course, to love every detail of that history, or that present; there is much sin there. But to love the church, despite its brokenness and, often, wickedness; to see the church, despite those things, as it is loved by the Lord Jesus. In practice, to lift our eyes beyond the confines of our own congregation and denomination, and to love the church as it exists in traditions which seem alien to us; to lift our eyes beyond the boundaries of our own culture, and to love the church as it exists in languages and forms which are foreign to us; to lift our eyes beyond our time, and to love the church as it stands in history as the monument to God's faithfulness and constant grace. To learn from ancient and alien forms, to sing the old hymns and the new songs and the songs from far away. To consciously stand in union and communion with those who have gone before on the road and those who walk the same road in very different places.