How to download an existing report from the JasperReports Server, and modify the query that is used by the report?

I am completely new to Jaspersoft. I have been working in Microsoft SSRS for some years. Today, our company's 
IT team has a task for me in Jaspersoft. They want to fix this immediately.

I have been given this link by the IT team:

http://xx.xxx.xxx.:8080/jasperserver/flow.html?_flowId=searchFlow

We have an existing report called TimeSheet that is scheduled to run everyday and this report is generated and sent via 
email to the managers every working day. The IT team needs to make a minor modification in the report so that 
all the employees are shown in the report regardless of whether the employees are present or absent. (Currently only those 
employees who are present are shown). This solution can be a simple one such as changing an INNER JOIN to a 
LEFT OUTER JOIN. I am told that a simple MySQL database contains the data for this report.

I have the following tasks before me:

1) I need to get into the existing Timesheet.jrsml (report) file in the Jaspersoft server

2) Then look into the query or stored procedure that runs this Timesheet report.

3) Modify the query and create a new Timesheet report that can be scheduled.

4) Deploy this new report into the server and schedule it.

5) Once the data is verified in the new report, the old report can be deleted.

The challenges I have are:

1) I find the Timesheet report in the TIBC Jaspersoft server (a web link). Is there a way I can download 
the existing Timesheet.jrsml file ?

2) How do I get the queries/ stored procedures that run this report?

When I right click the Timesheet report and go to Edit, I see the following:

Set up tab: I see a Read-Only resource ID called XYZ. Where do I find this resource ID called XYZ?

Datasource tab: I see a JDBC data source that exists in the Repository

Query tab: I see the 'Do not link query' chosen

Customization tab: None

More importantly, do I need to install tools such as Jaspersoft Studio, iReportDesigner etc locally in my 
machine to do this modification? Or can I do this change using the web browser link the IT team has provided:

http://xx.xxx.xxx.:8080/jasperserver/flow.html?_flowId=searchFlow

In the above link, I find the following:

1) root

  i)Reports

     a)Deployed Reports Folder

     b)Interactive

     c) some folders specific to our organization

I do not find the following under root folder:

  (ii) Analysis Components

  (iii)Content Files

  (iv) Data Sources

  (v) Images

  (vi)Themes

How to download template from JasperReports Server and modify it?