The credence table plays a prominent and practical role in the various Catholic liturgies as a storage area for various items that are not in immediate use but that will be or have been used in other parts of the celebration.
Preparing this for Mass (and other celebrations) and clearing up afterwards is part of your ministry as an altar server.
When setting up you will need to learn what will be needed for which celebration and how to arrange the various items on the credence table – see separate sheet. When you are doing this remember that people may already be arriving for Mass and seeking a quiet moment in prayer. When you are preparing things for Mass, try to do so without drawing attention to yourself. Although Mass has not started, you are already exercising your ministry as an altar server.
Similarly after Mass; many people may be leaving but others may have stopped behind to say a prayer of thanksgiving. When you take things from the sanctuary into the sacristy do so in a calm, dignified and respectful manner. The church and the sanctuary especially is holy ground, you are holding holy objects (the chalices may still have some Precious Blood in them), you are in the presence of the Blessed Sacrament reserved in the tabernacle – and you are a minister of the Church.