How to use custom fields in a sequence?

Your Saleshandy accounts will have three custom fields for First Name, Last Name, and Email and you will be able to create more custom fields as mentioned here.

Once a custom field is created, it can be used in the sequence. As shown in the below GIF file, when you upload a CSV file of contacts in a sequence, it will allow you to map the column header in your file with the custom fields in your Saleshandy account so that you can use the custom field variables to auto-pick the contacts' data from the imported CSV file.

You will be able to add variables (custom fields) in both the subject line and mail email body. You need to click closed curly bracket icons to insert the custom fields where you wish as shown below: 

When the sequence sends the emails, the system will automatically pick the data for each contact from the uploaded file and it will send the personalized emails to each prospect.