Which version are you using?
Cloud
Go to Settings > Apps, and in the sidebar, under CONNECTOR FOR SALESFORCE, select Bindings.
On the Bindings screen, click +Add Binding in the top right corner. If this is your first connection, the Bind your Jira project with Salesforce panel appears, providing a brief explanation of the step and a link to more information. You can also click +Add binding here to open the New binding dialog.
The New binding dialog appears.
Choose a Project you want to bind and the Connection you want to bind it to.
Click Add.
Connector begins automatically importing compact layouts. When finished, you are directed to the Mapping Configuration page to check your Mapping settings.
See Configuring Entity Mappings and Field Mappings.
Server
Go to Settings > Add-ons.
In the sidebar, under Salesforce, choose Bindings.
On the Bindings screen, click +Add Binding.
The New Binding dialog opens.
Choose a Project you want to bind and the Connection to which you want to bind it.
Click Add. When successful, you will be asked to create default mappings for supported issue types.
By default, you will be asked to map with Salesforce Case, but you can always map with other objects later.Choose the issue types you want a default mapping to create. Click Create.
If successful, the Bindings screen will display the binding you just added.