Loading of phloem means

Loading of phloem means pouring sugar into phloem.
Phloem is the living tissue in vascular plants that transports the soluble organic compounds made during photosynthesis and is known as photosynthates, in particular the sugar sucrose, to the rest of the plant. This transport process is called translocation.
The phloem is composed of still-living cells that transport sap. The sap is a water-based solution, but rich in sugars made by photosynthesis. These sugars are transported to non-photosynthetic parts of the plant, such as the roots, or into storage structures, such as tubers or bulbs.