Hi Jess,
We're glad you asked because this is an important feature that, unfortunately, not everyone knows how to use.
inwise Desktop Standard and Pro have "field settings" option under the "settings" button.
In the Pro edition you may customize your own field settings and in the Standard edition they are not customizable.
When uploading your list from excel, make sure your titles match the field setting titles. When adding recipients manually, add their details in the correct field settings, accordingly.

Once you synchronized between your field settings and recipients, you can start using the personalization feature.

When creating a new mail, wherever you want to add a field setting press "right click" and choose which field setting you want.
for example: #field1# may stand for first name.

We hope this explanantion has helped you.