Installation problem

I am a student and a new user. i am using r 4.0.2, when opening rnotebook ; I get a msg -

install.packages("xfun")
WARNING: Rtools is required to build R packages but is not currently installed. Please download and install the appropriate version of Rtools before proceeding:

please suggest solution,

RTools is an external program needed to compile packages from source code. See here.