Fusion makes it pretty easy, especially if you are using the wizard. Mines not dosing anything right now, but here's all you have to do.
Step 1. Open Fusion and make sure that you have your DOS tiles on your desktop. What you need to edit are the tiles that are circled below in red. Click on the gear icon to open the dosing head that you are working on.
Step 2. This is the interface you will get. Here you can click on the gear icon circled in red below to setup your dosing schedule.
Step 3. Here is where you just have to know what you are dosing and when you would like to dose it. This looks a little intimidating, but its relatively easy once you understand what it is asking you. The start/end times are the times you would like the dosing head to be active. If you want to dose calcium (for example) throughout the whole day (all 24 hours) then leave the times as set up below. If you only want to dose something during the day (from 5 am to 5 pm for example) you would set your start time to 05:00 and the end time to 17:00 (5pm military time). For action, you want the pump to ADD the material to the tank. The REMOVE command would be used for automatic water changes typically. Then you just imput the total amount of fluid you want dosed during the active time. So in the setup below, I want 40.0mL of Calcium dosed throughout the whole day. The Apex/Dos will determine the even number of dosages needed throughout the day to achieve this and will dose your fluid accordingly. After 24 hours, you will see the individual dosages on the home screen tiles, as well as broken up on this screen as well. Make sure to change the switches from OFF to AUTO on the home screen!
You can add multiple intervals and commands if necessary, as well as rename the DOS heads in there as well. A word of caution. Be sure to update your Apex firmware and calibrate the DOS before use. This ensures that the pump will accurately deliver the amount of material you want into your tank. Oh, and be sure to prime the dosing lines to the tank as well, otherwise your first several dosages wont do anything because you will be filling up the dosing tubes.
Good Luck!