Wind -
http://wiki.project1999.org/Broom_of_Trilon
Earth -
http://wiki.project1999.org/Shovel_of_Ponz
Fire -
http://wiki.project1999.org/Torch_of_Alna
Water -
http://wiki.project1999.org/Stein_of_Ulissa
The last two dont show a focus effect on them in the wiki, they should though. Not sure if that is a "classic" thing or what.
They work just by wearing them while casting your pet. As for level, iirc the above are for level 4 through 49 pets but again Im not sure what, if anything, this server being classic does to that information.