Whether a node type may be limited in access to a subset of the Users in the system depends upon its Visible to all (disable Access Control) setting, which may be found in the Data Hub under Other settings once you have selected a node type.
The default value is Visible to all and so you must change it to User/Team-permissions may be applied.
Once this is done, each individual node of that type will still be visible to all Users but now it will be possible to change that.
To do so, locate the node that you wish to restrict and then right-click on its title and click Set permissions.
Presuming that no permissions have yet been set on this node, you will see something like the following:
Had you tried to do this on a node whose type had a "Visible to all (disable Access Control)" setting of Visible to all then you would see the following message:
Switch the toggle to go from Public Access to Restricted Access and a search area will appear to enable you to select one or more Users and / or Teams that should be able to access the node:
Click the + button alongside each option to add that User or Team to the list of people that should have access. As you do so, that search result will disappear and the Teams and Users with access list above the search area will display the selections.
When first restricting permissions, a warning will be shown at the bottom of the popup - you must assign at least one User or Team (or revert back to Public Access) before saving.
After making selections, click Save (or click the X button on the popup to discard your changes). This node will now not be accessible by Users outside of those that you just assigned. If the node would otherwise appear in a set of results when that search is performed by a User who does not have access to the node then the node will not be included in the search results for that User.