Flowers should always be kept in a cool place, away from direct sun.
If your flowers are arranged in flower foam (Oasis) in a container (Basket, Box Arrangement, Ceramic) just take the flowers to your sink and use a glass or small watering can to add a little water each day. If this is done daily the flowers won't need much water.
If you have a bouquet that needs to go into a vase, the flowers need to go into water immediately - make sure the vase is clean and add cut flower preservative (or just a small drop of bleach) to the water then re-cut the stems (using sharp scissors or a knife, cut the stem on an angle) just before putting them in water.
Every three days replace the water - adding cut flower preservative or a small drop of bleach and again re-cut the stems on an angle just before returning the flowers to water.