To request money from someone on Sling:
Tap 'Request' at the bottom left of your transaction home screen
Select a contact from your list or find them using the search bar
Enter the amount and currency you want to request
(Optional) Add a photo or caption to your request
Review the amount and tap 'Confirm and request'
They'll receive your request and can choose to accept or decline it. If you have a pending request, you can tap on it to send them a reminder (once per day).