What is it saying you have to do?
It really should only be the following steps to install any Joomla component:
- Go to Administrator -> Extensions -> Plugin Manager and publish "System - Legacy" plugin.
- Go to Administrator -> Extensions -> Install/Uninstall and upload the component package file by choosing the file and then clicking the button "Upload File & Install"
- Go to Administrator -> Menus -> Mainmenu, click on the New icon in top right corner. Select Jobline from the list, type a name for the menu item and click on the Save icon.
Step 1 is only needed for components that need the legacy mode, and is only needed once.