TL;DR
Software testers are dealing with quite complex applications. To become a passionate software tester, you need to express your thoughts using words. Writing skill is an essential part of every software tester. The post is based on a remarkable book written by Chad Fowler, The Passionate Programmer.
When you write a test plan or test report, you do not want just to edit the template with bullet points. In those documents, you need to tell your software testing story [Bolton]. To be able to do that, you need to practice writing.
Blogging
Software testing is an excellent source for blog ideas. The problem could be if the client does not permit that you write about testing their software. If you do not get permission, you can start posing private WordPress posts. And share them only with your teammates or friends to get feedback. You can always just blog about the problem that you had and solved, not mentioning the name of the application or any other details. And publish that publically. You can write your testing story into Gdrive or simple text files. But you must start practicing writing. It clears your mind about the topic that you learned or the problem that you had. By explaining it in an essay, you are relearning the subject. For the blog option, I suggest WordPress. I tried Medium and Blogger, and trust me, WordPress should be your central point.
Grammar
Write text that is in correct grammar! This is essential. As I am not an English speaking person, I bought a Grammarly subscription. It costs money but integrates everywhere. If you are not good in English, write in your native language, but also grammatically correct. To learn the Grammar, read technically not related books in that language. This will keep your brain ready to process Grammarly exact text.
Typing
You need to learn to type with ten fingers and without looking at the keyboard. It took me five months practicing on Typing Academy. Open the account so you can monitor your progress. And practice every day, 15 minutes is enough! After a month, start using your skill. It will be overwhelming in the beginning, but even with errors, you will type faster.
This skill is essential because when typing becomes an automatic skill, your mind can concentrate on the writing topics.