You’ve got some nibs, a holder, a bottle of ink and some good quality, fairly smooth paper. Now what? The first thing to do is to familiarize yourself with those tools. A great way to do that is to try out the exercises as shown in this post.
I’ve not been able to find out much, if anything about Mr. Brown and his book, which is one of the best instruction books I’ve found. However, it can be downloaded as a pdf or in other formats from archive.org here.
Montague Ellwood’s book is also at the top of my list for excellent information and instruction. It is also available as a pdf download on archive.org here.
If you have some quite flexible nibs, you can do these exercises from J. Hullah Brown’s book.
Once you’ve started to feel comfortable drawing parallel lines in any direction, you can try these examples of crosshatching. This technique is the classic way to create value in black ink on white paper.
Lastly, have fun!