If you want to push to all users only one time: under apps, select the check box to the left of the app, then managed devices. then select your users. From there, select your action. FYI (the command will be sent to the devices, and as long as the devices are 'Active' and, if needed, you have the a valid APN (for apple devices).
If you want to make this change permanent, then under apps, select the check box to the left of the app, and then Assign. Under the Assignment model, change from On Demand to 'Auto'.
As always, make sure that you understand the changes you are making.