The use of assume here means "put on". So, "Please put on plastic gloves."

I think it is a mistranslation. I can only assume (!) that the person who wrote this intended it to mean 'Please put on plastic gloves'. 'Assume' can mean 'take on' in some contexts: for example, 'assume a responsibility' or 'assume a position'. Back in the 16th century, 'assume' could also be used for clothing. I'm guessing the the writer looked in a dictionary or thesaurus and made the mistake of thinking that this was modern English.

Yes, somebody must've made direct translation from polish. Thanks for answers

No that is incorrect.

No. Please wear plastic gloves. You can write "Please assume plastic gloves are up to no good." But on a sign that would be a fairly ominous warning. Is it a direct translation from Polish, and If so what was the original sentence?