At the presentation of the gifts, the offerings are brought forward: the faithful should present the bread and wine accepted by the priest or deacon at a suitable place. These are placed on the altar with the accompanying prayers.
The rite of carrying up the gifts continued the spiritual value and meaning of the ancient custom when the people brought bread and wine for the liturgy from their homes. From the GIRM #50.
If you want to participate in this ancient ritual, speak with one of the ushers.