Referring again to Karl Adam's book, one finds this lengthy but clear, further explanation of the Church Militant. I use this quotation to underline the necessity of gaining "merit". When the Church states that some are saved through the merits of the Catholic Church, we are reminded that we must gain merit in order for this to happen.
A strong Church Militant works on indulgences, reparative suffering, self-denial, and other means of building up the Kingdom of God on earth. Some go on pilgrimages, such as to Walsingham for indulgences. Many, if not most, of the serious members of the Church Militant say the daily rosary. Prayers for the sick or the dying provide indulgences. But, actions can also merit grace for those who seek the Truth.
One of the roles of the Church Militant is, simply, redemptive or reparative suffering. This type of suffering allows for the grace of God to flow into the lives of others. Novenas, as well as acts of penance, frequently are implemented by those in the Church Militant. Here is Adam again: