That video is a bit old, there is a new one: Even better, follow the instructions in the xschem tutorials: https://xschem.sourceforge.io/stefan/xschem_man/tutorial_xschem_sky130.html If you don't see the voltage source, delete it (click and press Delete), then press Insert key (Or Shift i) , press the Home button and navigate to

.../xschem_library/devices/vsource.sym

so you are placing the voltage source again. Then edit its attributes and add add its

value="....."

attribute. Note: I have updated today the

tb_reram

example to reflect @Barak Hoffer upates he made yesterday. See thread in #reram channel