[minnca]

I'd say a first step is to start building a body of writing samples. You can do this in a lot of different ways, but two suggestions are 1. adding or improving documentation for an open source project and 2. writing technical blog posts/articles/how-tos on topics that interest you and posting them on a personal website. Starting to build this body of work can also help you discern whether you even like technical writing. Then, I'd say the next step is to just start applying to technical writing jobs. (Maybe contract ones, if you'd like to just try it out first.) Since you have coding experience, I'd suggest targeting tech writing jobs that require proficiency with languages you're familiar with or deal with technologies in domains you're interested/have experience in.