By default, all issues would be linked with a Company associated with a Jira user - issue reporter. 

If you want to link issues and companies more flexibly, you can switch to Manual way in Apps/Teamlead CRM/Settings/Company Autocomplete. Once you've changed the way, you would be able to link issues with a company directly in the issue. Please note: we do not recommend to switch several times between the way of company detection because it may cause of out of sync links between companies and issues.