how to process working visa, im already here in china with tourist L type.

You should first prepare the required materials for work Z type including your passport and copy of its data page, the filled-out application form with a passport-style photo glued, valid temporary accommodation registration form, alien employment permit and an invitation letter from a duly authorized unit. And then go to the exit and entry administration of the local PSB to try to convert tourist L type to work Z type.