Once you've logged into WordPress, you'll be taken to
the WordPress Dashboard. Take a look at the sidebar
menu on the left. Near the top is an option labeled Posts.
Click it! From the submenu it opens, simply click
"Add New" and you'll be taken over to the editor where
you can type up your blog.

If you're not ready to sit down and finish your blog - but
just want to get something basic started - you can also
use the Quick Draft box right on the dashboard. 

The editor should be fairly familiar to you. It functions just
like any basic text editor/word processor. There are a few
exceptions to that, however. 

This particular editor utilizes blocks, allowing you to specify
portions of your post to be text, images, galleries, etc. There
are two ways to add a block to your post.

The first is to just click on the body of the post and type a
slash - /. This will give you a dropdown menu to select from.
The other way is to click the black box with the white plus
sign. This will give you options to add a block or alter an 
existing block. 

Take some time to familiarize yourself with the sidebar
options on the right side of the screen. This is where
WordPress has placed options regarding typography and
other formatting tools. It will also provide you with some
options about your post itself, including tools that give you
options to include categories for your post, to change the
author, and more. 

While WordPress does save your work automatically, it's
always a good idea to click "save draft" occasionally to
ensure that you work will be there for you later. We also
recommend previewing your work frequently to ensure that
your formatting is as you'd like it to be. The preview button
will ask you to specify what type of device you want it to
emulate for your preview. Typically it is safe to just preview
it as it will be seen on desktop. Simply select "desktop" and
click "Preview in New Tab" to see how your post will look
to the public.