You have a couple of options which depend on the size your data (number of rows & number of columns).
1. If the size of your data is small , you can put the additional data into an excel sheet , copy the data & paste into Sharepoint List in the GRID VIEW . "Edit grid view" helps you to manipulate a sharepoint list just like an excel sheet. This is the easiest & quickest option. 2. If your data is considerably huge in terms of columns and rows , you can use POWER AUTOMATE to read data from excel sheet and upload it into SP list. This option requires you to be familiar with power automate and some basic programming skills.