Updating Jamroom 6 to 7, or within Jamroom 7, is a normal Marketplace update: see Keeping Jamroom Up to Date. This page is for a site still on Jamroom 5, or one that hasn't been updated for a long time.
Jamroom 6 changed the Timeline a lot. If your skin overrides the Timeline list (jrAction_item_list.tpl), compare it with the new item_list.tpl on ACP > Modules > Profiles > Timeline > Templates, and bring the changes in. See Keeping a Cloned Skin Up to Date.
Jamroom 4 can't be updated: its content is imported into a new site. See Jamroom 4 Import.