In this poem, the main example of personification that stands out is that Spenser has the tide, or the waves, speak to him. Personification is giving inanimate objects human-like traits, so a wave speaking is literally impossible, but figuratively interesting. The poem states that the tide states of Spenser writing his love's name in the sand, "'Vain man,' said she, 'that doth in vain assay,'" then goes on to tell him that trying to immortalize his love by writing her name is an exercise in futility. Spenser disagrees, saying that writing this poem will be the way his love will become immortalized-very true, considering we are talking about it 400 years later.
The main personification is in the tide, or the wave, and how Spenser has it speak to him. I hope that helped!
What is the main theme in Edward Spenser's "Sonnet 75"?