Coupling PLASIM and PUMA requires some handwork currently.
This is a quick introduction:

 1) Start most.x and select:
    PUMA, CPU's=1, Instances=2, Orography, Annual Cycle, NSYNC=1, SYNCSTR=0.1
 2) Click on "Save and Exit"
 3) Copy the contents of puma/run to a new directory, say $WORK/run
 4) PUMA will get the instance number #1, so files ending with _01
    are necessary for PUMA

 5) Start most.x and select:
    PLASIM, CPU's=1, Instances=2, NSYNC=1, SYNCSTR=0.1
 6) Click on "Save & Exit"
 7) Change to plasim/run
 8) Copy the plasim executable to $WORK/run
 9) Copy all *.sra files to $WORK/run
10) Copy all *_00 files to $WORK/run
11) Change to $WORK/run
12) Edit puma_namelist_00 (for PLASIM)
13) Insert NEQSIG=1
14) Insert N_DAYS_PER_YEAR=360
15) If you want to run with (two!) GUI's then copy
    from puma/dat/GUI.cfg to $WORK/run/GUI_01.cfg
    from plasim/dat/GUI.cfg to $WORK/run/GUI_00.cfg
16) Write a new run script for organizing output from both models,
    plasim files have the appendix "_00" and puma files "_01".
17) Or try it out b directly calling:
    openmpiexec -np 1 most_plasim_t21_l10_p1.x : -np 1 most_puma.x 32 10
18) Any help, e.g. a new runscript for coupled runs is appreciated.