Download the latest version of R program from http://cran.at.r-project.org/bin/windows/base/release.htm and install on your computer.
Installation files of the JUICE program can be downloaded from http://www.sci.muni.cz/botany/juice/?idm=3. If you have already installed the JUICE program on your computer, you may want to update it (in JUICE menu go to Help > Quick JUICE update).
First step to use the JUICE-R function is to link JUICE and R program by setting up the R directory in JUICE program. Start JUICE program, and in menu File > Options > External Program Paths > R project specify the address of Rgui.exe file1). This file is usually in
c:\Program Files\R\R-x.xx.x\bin\x64 folder (if you run 64-bit version of R) or in
c:\Program Files\R\R-x.xx.xx\bin\i386\ folder (if you run 32-bit version of R).
R-x.xx.xx is the R version you are currently using (e.g. R-3.0.2).