Currently, Typing.com does not have an "assign lesson" feature.
You can either instruct your students verbally in regards to which lessons you wish them to work on, or you can enable/disable the lessons and this could serve as a workaround.
To enable/disable lessons, please follow these steps:
Pro-Tip: You can change the settings for the whole class, not for individual students.
Step 1: Log in to your account here.
Step 2: Go to "My Classes" on the top menu.
Step 3: Locate the name of class and click "View" on the right side.
Step 4: Click Settings, and then click the "Lessons" tab.
Step 5: Select which lessons are active. Check to display or uncheck to hide all lessons, sections or individual lessons.
Step 6: Scroll down to the bottom of the page and click "Save all Changes"
That's it! Now you know how to enable/disable lessons. 😊