Create and then select an initiative. You should have a screen which shows "Initiative" towards the top left.
Scroll down to the box which says "Do Next".
Select "Add Related People" (3rd from the bottom).
Enter the name of a person/stakeholder. As you type, the names of existing people will appear in the dropdown list below. If you see the name of the stakeholder simply click on it to add it. If you don't, finish typing the name of the person and press enter.
The name of the person/stakeholder will then appear above the input box. You can select the RASCI role from the dropdown list next to the name.
You can add as many stakeholders to the initiative as you need. You can then repeat the process for your other initiatives.
Once you're complete, you can return to the Strategy Board to run the Initiative RASCI.
You can do this at any stage to confirm that you have correctly identified all the stakeholders required for the success of your initiatives, identify and correct any gaps.