Everything I have read is that journaling is a great practice for self awareness, spiritual and psychological grown, place to process things in your life, etc.
I also have read the actual physical connection from hand to pen to paper is the best way of bringing your mind-body-soul together. But if that is keeping you from writing at all then do whatever is convenient for you.
When? Most experts say it should be daily or at least on a regular basis and “when it is needed.”
What? There are many books to guide you on that. My favorite is “Writing Down Your Soul: How to Activate and Listen to the Extraordinary Voice Within” by Janet Connor. There is “The Artist’s Way: A Spiritual Path to Higher Creativity” which talks more overall about creativity but there is an exercise called “morning pages” which tells you to write three pages free hand every morning in stream-of-consciousness style.
I think the key to all of this is that since it is so simple, that it really does not require any elaborate or expensive equipment to do then you just got to do it without overthinking about it. It is just important to do it on a regular basis.
Having a set time of day and place to write helps to make it easier to make it part of your daily routine to keep at it.
Mark