Four things, and you probably own two of them.
Paper
Plain, unlined, A4 or bigger. Bigger is easier at the start: a large sheet leaves room for the line to go somewhere unexpected, and a small one fills up before you have got going.
The one thing that matters is thickness. Thin printer paper lets a marker bleed through to the next sheet and to the table under it. Anything sold as sketch paper is fine.
Something to draw the line with
A black fine-tipped marker or a liner, somewhere around 0.5 to 1 mm. It should move without you pressing, and it should not run out halfway through a session — you will be drawing more line than you expect.
A gel or ballpoint pen works. A pencil does not, really: it smudges under your hand and the line goes grey where you want it dark.
If you have a second, thicker marker, keep it. It is useful in module 2, where some crossings are small enough to fill in rather than draw around.
Colour, if you want it
Optional, and not needed until module 3. Coloured markers, felt tips or pencils all work; five or six colours is plenty, and a set of forty is a decision to make forty times.
A drawing left black and white is finished, not unfinished.
Time and a flat surface
Twenty minutes and a table. Not the corner of a kitchen counter with one hand free — rounding takes both your hands and your attention, and the practice gets short-changed if you are standing up.
There is one rule about time and it arrives in module 2: a drawing you start, you finish the same day. Worth knowing now, so you can pick the hour.
Your practice
Put your kit together and take a photograph of it on the table where you are going to work.
That photograph is your first journal entry. Nothing depends on it and there is nothing to get wrong — which is exactly why it is the entry to make first, rather than finding out how the journal works with a drawing you care about in your hand. Photos from a phone are fine; the size is handled for you.
In the note, write down what you already had and what you had to go and find.
Next: the line.