You can have apps, documents, folders, or server connections open automatically whenever you log in to your Mac.
Add or remove automatic items:
1. Choose Apple menu > System Preferences, then click Users & Groups.
2. Select your user account, then click Login Items at the top of the window.
3. Do one of the following:
- Add a login item: Click the Add button below the list of items, select a document, folder, app, server, or other item, then click Add.
- Remove a login item: Select the name of the item you want to prevent from opening automatically, then click the Remove button below the list.
- Hide a login item: If you don’t want an item’s windows to be visible after login, select the Hide checkbox next to the item.
Note: Hide does not apply to servers, which always appear in the Finder after login.
The above is an excerpt from the full support article provided by Apple Support, found here: https://support.apple.com/kb/PH25590?viewlocale=en_US&locale=en_US