Hi kareena,
Thank you for reaching out and we hope you are in good health. We appreciate your interest in Samsung home appliances, specifically with Samsung - 4.2 Cu. Ft. High Efficiency Stackable Front Load Washer with Vibration Reduction Technology+ - White.
Yes, you can still add some forgotten items are the cycle starts. Just press the Start/Pause button. I have shared the user manual link below. Please access the link and turn to page 19 for loading the washer.
https://downloadcenter.samsung.com/content/UM/201904/20190416101808805/BETTER_WF42H5000-DC68-03397A-14_A2.pdf
Please feel free to communicate with us through the channels below if you have additional questions.
1. Facebook Messenger: http://m.me/samsungsupport
2. Twitter: https://twitter.com/messages/compose?recipient_id=18768513
3. Samsung Community: https://us.community.samsung.com/t5/Samsung-Community/ct-p/us
Your reference number: 1144416176
Leo