Better help

htdocs/langs/en_US/projects.lang

@@ -249,7 +249,7 @@ TimeSpentForInvoice=Time spent
 OneLinePerUser=One line per user
 ServiceToUseOnLines=Service to use on lines
 InvoiceGeneratedFromTimeSpent=Invoice %s has been generated from time spent on project
-ProjectBillTimeDescription=Check if you enter timesheet on tasks of project AND you plan to generate invoice(s) from the timesheet to bill the customer of the project (do not check if you plan to create invoice that is not based on entered timesheets).
+ProjectBillTimeDescription=Check if you enter timesheet on tasks of project AND you plan to generate invoice(s) from the timesheet to bill the customer of the project (do not check if you plan to create invoice that is not based on entered timesheets). Note: To generate invoice, go on tab 'Time spent' of the project and select lines to include.
 ProjectFollowOpportunity=Follow opportunity
 ProjectFollowTasks=Follow tasks
 UsageOpportunity=Usage: Opportunity