Go to Extentions > Installer and upload payssion.ocmod.zip.

Go to Extentions > Payments and find Payssion. Fill in API Key and Secret Key which you can find at your Payssion account, select the proper status for the fields of Order Status, Pending Status, Canceled Status, Failed Status and Chargeback Status and click Save button. Regarding the status, you can refer to the following: Order Status: Processing
Pending Status: Pending
Expired Status: Expired
Canceled Status: Cancelled
Failed Status: Failed
Chargeback Status: Chargeback

Activate the alternative payment methods you want to use. Take paysafecard for example. Click edit after installing paysafecard (via Payssion), then select Enabled for the Status option, and click Save button.