There are 3 tiers of Credits within LIGR and an article explaining those can be found here.
In order to add credits into your account follow the steps below:
Hover over the Profile icon in the bottom left of the screen.
Select Credits.
At the next screen, select Buy Credits.
Use the slider to select the amount of credits that you wish to purchase. In the below image, 50 Streamer credits have been selected.
Enter the card details that you wish to use to complete your purchase.
When entered, click Buy Credits.
NOTE: Auto Top-Up is available so that you never have to worry about running out, BUT the user must have their card details on file.