Normally this would be enough, I think:
The '0' indicates that an open string is to be used (in this case the high 'e' string). And from the context you would infer which string to use for the other 'e'.
If you want to be more explicit that the other 'e' should be on the b-string you could notate this as well:
The number with a circle indicates which string to use, counting from high to low.
Perhaps in this case you want to be more consistent and use the string number notation for both notes:
You may want to notate the two notes in different voices:
And finally, using tab notation you would automatically show which string to use:
I left out the notation of which pluck fingers to use for several reasons: I didn't think it was essential for your question. And I wouldn't be explicit on that for just plucking a chord, maybe for a more complex fingering pattern. Furthermore the score examples would be unnecessarily crowded, I think.
Nevertheless, to notate pluck finger (or stroke finger) there's a convention to use the letters 'p', 'i', 'm', 'a' and 'c':
thumb = p = pulgar, 1st finger = i = índice, 2nd finger = m = mayor, 3rd finger = a = anular, 4th finger = c = chiquito