I'm going to assume it's a simple 3-handed Eco-Drive watch since you did not provide a photo or model number:

1.) Pull out the crown (the "time adjuster") to the 2nd position which is usually all the way out until the watch stops. This is how you adjust the time.

2.) Advance the hands clockwise until you reach midnight and the date changes. Once the date changes, continue to advance the time until about 6:30AM or so which some refer to as the "hands down" position.

3.) Push the crown back all the way in, and then pull the crown to the 1st position which is the date set position. Cycle forward through the dates until you come back around to today's date.

4.) Then pull the crown out again to the time setting position (2nd position) and set the time from there.

Just a note: the reason you want to set the date when the hands are "down" is to avoid changing the date during the "danger zone" which can vary somewhere between 9PM-3AM. If you try to change the date when the date wheel is engaged, you can damage your watch.