Installing rstudio linux

Hello. I need to check a linux formatted hdd ext4 for deleted files on my laptop w/ ubuntu 1710.

I see that I need to download "R' first and then the version for ubuntu, either 32 or 64 bit. After I downloaded the ubuntu 64 bit, i see that it shows the size as 456mb whereas the website shows it should be about 97mb. Should I be concerned that I have not downloaded the actual file but a "hacked" type file?

I see that I have to download the following first: rstudio 301.
For r studio 301 - I used the command line entries but they did not work (ie: deb https://<my.favorite.cran.mirror>/bin/linux/ubuntu artful/). So I scrolled down to here and did the following:

sudo apt-get update
sudo apt-get install r-base

I had first tried the command line entries above this but kept getting a 'no such file / directory'. So I don't know for sure if the "sudo" command lines were all that I needed or the correct entries. They did process successfully.

Then i dowloaded the ubuntu 64 bit file and it is a tar.gz file and i extracted the contents. I see a "install" file there. I imagine that I should click on that...? I don't want to until I hear back from you about the "456mb (1,827 items) - rstudio-1.1.442" as that does not make sense and i do not want to damage my computer if that is a 'false' file.

I do not have access to a windows os to use rstudio for windows or I would. I get the feeling that using rstudio in linux isn't really that difficult, but I do need some help.

I am new to linux.

I would appreciate any help!
Thank you!