RHEL comes with preconfigured repo, you can search for the desired packages and install them using yum package manager.
To do so, first run ( to search gcc )
$ sudo yum search gcc
which will show you a list of available packages with the matching name
============================ Name Exactly Matched: gcc =============================
gcc.x86_64 : Various compilers (C, C++, Objective-C, ...)
gcc.x86_64 : Various compilers (C, C++, Objective-C, ...)
gcc.i686 : Various compilers (C, C++, Objective-C, ...)
=========================== Name & Summary Matched: gcc ============================
gcc-c++.x86_64 : C++ support for GCC
gcc-c++.i686 : C++ support for GCC
gcc-gdb-plugin.x86_64 : GCC plugin for GDB
gcc-gdb-plugin.i686 : GCC plugin for GDB
gcc-gdb-plugin.x86_64 : GCC plugin for GDB
gcc-objc.x86_64 : Objective-C support for GCC
...
Install the package you need by running ( to install gcc-c++ )
$ sudo yum install gcc-c++
It will the packages to be installed and ask for confirmation.
Dependencies resolved.
====================================================================================
Package Architecture Version Repository Size
====================================================================================
Installing:
gcc-c++ x86_64 8.3.1-2.fc29 updates 12 M
Transaction Summary
====================================================================================
Install 1 Package
Total download size: 12 M
Installed size: 29 M
Is this ok [y/N]:
NOTE: Steps mentioned above will install latest available version of the package.
Install a particular Version of a Package
Install all development tools