Handling pop-up Authentication windows in Rselenium

Does anyone in this community have any idea how handle (how key in username and password) in pop up window when web-scrapping with RSelenium? I am trying to log into the following-data portal and automate bulk download.
below is the webpage
https://land.copernicus.vgt.vito.be/PDF/portal/Application.html#Browse;Root=512260;Collection=1000084;Time=NORMAL,NORMAL,-1,,,-1,,