Step 1: Step 1: Login into portal.office365.com
Sign in with your Login ID and Password.
Step 2: When entering account click on Admin as shown into the picture.
Step 3: On the home page click on the add new user tile as shown in the picture.
Step 4: After click on the new user a window will appear Enter all the Basic Information of user.
Step 5: Now click on the Next and on the next page assign the Product License if you want.
Step 6: In optional setting we have option to assign user as Global Admin, if we want this, we can do that otherwise choose User option only and click on Next.
Step 7: In the last page it will show all the summary of user like username password etc. click on Finish and now we successfully created a new user.
Here is user created screen shot.