Visit CP2K download page and download the source code by any means you prefer.

If one get the distribution from Sourceforge website, after download cp2k-2.x.x.tar.bz2, unpack the archive files using the command given below

tar -xvf cp2k-2.x.x.tar.bz2

The latest and all prior versions are available from the CP2K SVN repository.

Check out only a needed branch (the branch will then be in cp2k/cp2k).

• current trunk:

  svn checkout http://svn.code.sf.net/p/cp2k/code/trunk cp2k

These branches can be updated to their latest version in the following way:

cd cp2k/cp2k
svn update

Alternatively, you may restrict the download to the folder cp2k/cp2k containing source code, tools, and test inputs, e.g. for the trunk version use

svn checkout http://svn.code.sf.net/p/cp2k/code/trunk/cp2k cp2k

Analogous checkouts work for the branch versions.

The Subversion (svn) program must be installed on your machine for this to work.

An example CP2K ARCH file for a serial build of CP2K on Mac is as follows:

# With GCC 4.9 or later, for gcc and gfortran
# libxc is installed in LIBXC_INCLUDE_DIR / LIBXC_LIB_DIR
# libint is installed in LIBINT_LIB_DIR
CC       = gcc
CPP      =
FC       = gfortran
LD       = gfortran
AR       = ar -r
RANLIB   = ranlib
DFLAGS   = -D__NO_STATM_ACCESS -D__ACCELERATE
FCFLAGS  = -I $(LIBXC_INCLUDE_DIR) -O2 -ffast-math -funroll-loops \
           -ftree-vectorize -ffree-form $(DFLAGS)
LDFLAGS  = $(FCFLAGS)
LIBS     = -framework Accelerate

Remove the -DLIBXC -DLIBINT flag if you compile CP2K. Save it as Darwin-IntelMacintosh-gfortran.sopt in the cp2k-x.x.x/arch directory alongside the other ARCH files.
Launch the Terminal and change the working directory to cp2k-x.x.x/makefiles. Type make command as follows:

make ARCH=Darwin-IntelMacintosh-gfortran VERSION=sopt

It may take quite a while until a compilation is completed. If you have a multi-core machine you may use e.g. make -j 4 to compile in parallel with 4 tasks.
If you find cp2k.sopt in cp2k-x.x.x/exe directory, then compilation is successfully done.