Lekato sent me the manual - as I suspected it's pretty much 1. plug in. 2. turn on (3. make sure they're on the same channel) but I've attached it for anyone who wants it.
It does GENIUNELY say attach the transmitter to "guitars, mussels, blowtorches etc" - I would strongly advise that you do not attempt to attach it to a mussel or a blowtorch.
Anyone who can't work out that the one with the picture of a guitar on goes in the (Bass) guitar and the one with the picture of the speaker on goes in the amp (even with dymo and/or colour coded labels attached) should present themselves to their nearest freelance vivsectionist, police station, glue factory or tannery.
I will ABSOLUTELY plug them into the wrong things at my next gig.
WS-90 USER MANUAL M01582N.pdf