Guile can be obtained from the main GNU archive site ftp://ftp.gnu.org or any of its mirrors. The file will be named guile-version.tar.gz. The current version is 2.1.8, so the file you should grab is:
To unbundle Guile use the instruction
zcat guile-2.1.8.tar.gz | tar xvf -
which will create a directory called guile-2.1.8 with all the sources. You can look at the file INSTALL for detailed instructions on how to build and install Guile, but you should be able to just do
cd guile-2.1.8 ./configure make make install
This will install the Guile executable guile, the Guile library libguile and various associated header files and support libraries. It will also install the Guile reference manual.
Since this manual frequently refers to the Scheme “standard”, also known as R5RS, or the “Revised^5 Report on the Algorithmic Language Scheme”, we have included the report in the Guile distribution; see Introduction in Revised(5) Report on the Algorithmic Language Scheme. This will also be installed in your info directory.