An edition is automatically checked-out by you when you open it.

To change it's check-out status, close the edition.

It is not possible to open an edition only for viewing, except when someone already checked out the edition - if you try to open it, you'll be prompted whether you want to open is only for reading.

An edition, opened only for reading, shows in the right side of the status bar, the yellow label "Read-only".

See also

Change check-out status of pages, Change check-out status of layers, Check-out of all pages quickly