How to Enable Salesforce1 For Community User?

Please follow these steps:-

1. From Setup, enter Mobile Administration in the Quick Find box, then select Salesforce1 Settings and verify that Salesforce1 access is enabled for your organization.
2. For automatic access to the Salesforce1 mobile browser app while accessing the community, select Salesforce1 User on each external user record. (Salesforce1 User is automatically t turned on for internal users when the mobile browser app is enabled.)
Without this setting, external users with communities licenses must append /one/one.app to the community URL (for example, https://universaltelco.force.com/customer/one/one.app) to use Salesforce1.
3.For access via the Salesforce1 downloadable apps, grant the “API Enabled” profile permission to external users with communities licenses.
4. Communities that use the Salesforce Tabs + Visualforce template are supported in all of the Salesforce1 apps.
5. Communities that use a Community Builder template, such as Koa, Kokua, or Napili, contain rich styling that doesn’t display in Salesforce1. Templated communities are responsive and it’s best to access them directly from a mobile browser using community URLs.
6. External users who belong to multiple communities or users from your organization who also belong to one or more communities can use the drop-down menu at the top of the Salesforce1 navigation menu to access communities.