How Do I Say "It's Beautiful" In Spanish?

To say something is beautiful, you can say:

'Es hermoso (-a)'
or
'Es bello (-a)'

For example, for a beautiful house, you can say,
Es una bella casa.

For a portrait:
Es un bello retrato.

If you want to just comment on something a person is showing you, you may just say, 'It's beautiful.' which is 'Es hermoso' or 'Es bello.'

Be sure that you get the gender right in your situation. Adjectives end in -a for female nouns and in -o for male nouns. That is usually easy because the nouns also follow the same most of the time. Cara (face) is feminine, porta (door) is also feminine whereas boligrafo (ballpen) and telephono (telephone) are masculine.