Download either the 'Arena' or 'Tarrasch' GUI.
(Most chess engines do not come with an interface.)
Arena is infinitely configurable, and thus a minor PITA to get started with. Tarrasch has significantly fewer options to hunt down.http://www.triplehappy.com/http://www.playwitharena.com/
Now find and install an engine.
Grab Stockfish, a longtime resident in the World Top 5 list. (#2 at the moment, I believe.)https://stockfishchess.org/
An older version of Komodo, V7 at the moment.https://komodochess.com/
Other strong freeware engines include Fire, Gull, Equinox, and others as seen here.http://www.computerchess.org.uk/ccrl/4040/http://chesslogik.wix.com/firehttps://sourceforge.net/projects/gullchess/files/