Problem installing access to Github repository

Hi,
I have been trying in all different ways to be able to start a project in Rstudio that can be saved in my repository on Github but nothing is working.
I tried to install git.exe on my laptop, but keep getting git.cmd.exe which is not accepted by Rstudio instead of git.exe, no matter which options I select during the installation.

Then I tried this command:

devtools::create("GitHub - nancywahl/DataSci_CrimeStats")
(from something I saw on this support site, but I'm probably missing some step.)

Error: DataSci_CrimeStats.git is not a valid package name: it should contain only
ASCII letters, numbers and dot, have at least two characters
and start with a letter and not end in a dot.

Any specific suggestions? I really need a step by step guide to this process. Thanks!

Nancy J