You can enter income from the Dashboard or under Income & Expenses.

Clicking on the green +Income button (opens "Add Income" box)

Click in the Description field and select an Income source listed, (You can add any additional self-employed income by selecting "Custom" then adding the new description).
The new description will be added to your list.

You can also make an Income a "Recurring" entry, so you don't have to enter it every week/month.

Check all the fields are entered, then click "Save".