In my local game, we have been using Psionics since the beginning of 5th edition as House Rules. These are some of the rules that we have been using during our games. These are based heavily on the 3.5 rules for D&D.
To use a psionic item, it must be activated, although sometimes activation is accomplished simply by picking up an item or putting it on. Some items, once they are attuned, function constantly. In most cases, using an item requires either a normal Action. This, of course, is at the discretion of your Dungeon Master.
Activating a psionic item is a standard action unless the item description indicates otherwise. The manifesting time of a power is the time required to activate the same power in an item, whether it’s a power stone, a dorje, or a psionic tattoo, unless the item description specifically states otherwise.
The four ways to activate psionic items are described below.
Power Completion: This is the activation method for power stones. Activating a power completion item is a normal Action. The idea behind this is that the power within the stone is missing only the final part to manifest the power. The user must simply manifest the power. Powers stored in power completion items are usually not augmented, because the manifester level of such an item is assumed to be the minimum necessary to manifest the stored power.
Power Trigger: This is the activation method for dorjes and psicrowns. It requires the special knowledge of power manifestation that a character of the appropriate class would know, and the formation of the appropriate command thought. If a power is on a character’s power list, the character knows how to use a power trigger item that stores that power. The user must still determine what power is stored in the item before she can activate it. Activating a power trigger item is a standard Action
Command Thought: If no activation method is suggested either in the psionic item description or by the nature of the item, assume that a command thought is needed to activate it. Command thought activation means that a character mentally projects a thought, and the item activates. No other special knowledge is needed. Activating a command thought psionic item is a standard Action. Sometimes the command thought to activate an item is mentally imprinted within it and is whispered into the mind of a creature who picks it up. Other items are silent. These items usually require attunement through study.
Use-Activated: This type of psionic item simply has to be used to activate. Use activation is generally straightforward and self-explanatory. Many use-activated items are objects that a character wears. Some items made for wearing must still be activated. Although this activation sometimes requires a command thought, usually it means mentally willing the activation to happen and does not require an Action. The Action will be used in actually using the item. These types of items are usually limited in nature and have “charges” that diminish as the item is used, and the item hen crumbles to dust on the last use of a “charge.”