Dear Marek,
the steps for importing and using a new application library are as follows:
Step 1: Import the abl file containing the application library as shown in the following
video (from your post we assume you have already completed this step)
Step 2: Create a new user for the newly imported application library as shown in this
video. In the dialog for creating a new user, select the newly imported library in the drop-down-list "Application Library".