I think you are confused because of the New Testament usage of the word Saint - which is all those who follow Jesus and are part of His kingdom.
At the time, since few Christians had died, this applied largely to the earthly members of the Church. In this way the word “Saint” was used honorifically of all earthly Church members (even though some of those physically present were probably not - or would not remain - Saints on the road to heaven.) The Catholic Church accepts this manner of referring to the Saints too - as including the righteous members of the Church on earth. However this is not the only meaning.
**Saints are also - definitively - those members of the Church who HAVE OBTAINED THEIR REWARD IN HEAVEN. **This usage is one that many protestants (though not all) later abandoned. However in the Catholic Church, and other Churches of Apostolic origin, such as the Orthodox, the people we know for certain are Saints, are those in the direct presence of God in heaven now.
So, How do we know which Saints are in heaven now? The church determines this by seeing which people were touched by holiness, have lived a good and holy Christian life AND, who by their heavenly intercession have obtained miracles from God. The process of canonisation seeks evidence of this, and declares whether certain persons are in the direct presence of God in heaven and therefore heavenly Saints - such as the figures described in Revelation, who offer prayer to God for humanity.