Touch the chevron at the bottom right and then touch Find & Replace:
Choose the operation you want:
To find a word, type it into the first field at the top of the screen and touch the left- or right-pointing arrow to find the previous or next occurrence of the word:
To do a find and replace, into the first field enter the word to be replaced and into the second enter the word that will replace it:
Touch the left- or right-pointing arrow to find the previous or next occurrence of the word. Choose Replace if you want to make the switch or touch the right-pointing arrow to skip this occurrence and find the next one.
Note that Final Draft Go does not have the ability to do a global find and replace.