@User are you able to run the example simulation above ? you need to place a xschemrc in the directory where you launch xschem and have these 3 lines, with the correct paths for your installation:

lappend tcl_files scripts/sky130_models.tcl
set SKYWATER_MODELS ~/projects/foundry/skywater-pdk/libraries/sky130_fd_pr_ngspice/latest
set SKYWATER_STDCELLS ~/projects/foundry/skywater-pdk/libraries/sky130_fd_sc_hd/latest

the sky130_models.tcl is located in the xschem_sky130/scripts directory. If you are running in a different directory set the full path to it :

lappend  tcl_files  /path/to/sky130_models.tcl