Great that you now know how to use giveme! Now the jeija mod:
If I understood you correctly you dowloaded this one: jeija05.tar.gz
I downloaded it too and extracted in my mods/minetest folder of an older minetest version:
Then I did some trials and errors. What worked was copying the experimental mod that I found here:
into the same folder as jeija:
I managed to give myself 10 mesecons, typing /giveme jeija:mesecon_off 10
Maybe there are more solutions, I don't know. But this one worked (on my computer).