You should click on the Share with Reviewers button in the Sharing Permissions panel as shown below. It is located on the left in your experiment view. This will generate a secret code, which you are supposed tell the editor, who will pass it onto the reviewers, who will use it to get anonymous read only access to your uploaded data.
Once you have clicked on the
Share with Reviewers
button, the Sharing Permissions panel will change slightly as shown in the second figure below.
You can click on the
link and it will display the code again so that you can copy and paste it elsewhere.
More details are provided in Spidlen et al., Preparing a Minimum Information about a Flow Cytometry Experiment (MIFlowCyt) Compliant Manuscript Using the International Society for Advancement of Cytometry (ISAC) FCS File Repository (FlowRepository.org). Current Protocols in Cytometry, UNIT 10.18, July 2012. Specifically, it is described in Basic Protocol 2: FlowRepository Data Upload and Annotation, Section Share your dataset with reviewers (Steps 70-72).