Turning your design into a written out pattern can seem daunting but there are great tips out there for helping you break it down into doable tasks. It's also a good idea to get your pattern looking its best before sending it to your tech editor. Sometimes it is necessary to ask a designer to have another look at their pattern before it is ready for editing.
Frenchie of Aroha Knits has a great pattern writing tutorial here: Knitting 101: How to Write a Pattern or How I Write Mine.
Joeli of Joeli Creates offers a checklist of things to do to get your pattern ready for your tech editor and reasons why it is important to do so: Designer Checklist.
On my Tech Editing Services and Testimonials page I've laid out what I offer as a tech editor. Sometimes designers ask for services that are not in the usual realm of a tech editor--for example, pattern grading. (Not something I currently offer but am open to learning in future!) There are some tech editors who offer this service but it will likely be a separately charged service as it falls under the realm of pattern writing rather than editing. Since this is the case, the tech editor will hire another editor to check their work.
There are plenty of other links and books out there to help you on your way to designing, so do as much research as you can!