( وَجَاءَتْ سَيَّارَةٌ فَأَرْسَلُوا وَارِدَهُمْ…) (And there came a company of travelers; then they sent their water drawer…): The Arabic word (a company of travelers) refers to a caravan due to their long journey. They were heading from Madyan towards Egypt. They stopped at the well and sent they sent one person to bring them water from that well.

(… فَأَدْلَىٰ دَلْوَهُ ۖ قَالَ يَا بُشْرَىٰ هَٰذَا غُلَامٌ…) (… and he let down his bucket. He said, “Good news! Here is a boy.”…):

This person threw the bucket into the well to fill it with water, and Yusuf (PBUH) clung to it. When the water-drawer found a young beautiful boy clinging to his rope, he cried out: ‘Good news! Here is a boy’. The Quran does not explain how he came out or how he clung to the rope.

(… وَأَسَرُّوهُ بِضَاعَةً…) (… And they concealed him, [taking him] as merchandise…): That is, they concealed him in the caravan, as they wanted to sell him in Egypt.

(...  وَاللَّهُ عَلِيمٌ بِمَا يَعْمَلُونَ ) (…  and Allah was knowing of what they did):  Allah (swt) fully knew what they did.