The title of the poem is actually The Passionate Shepherd to His Love.
Sensuousness is a reference to all things which, in an aesthetic sense, appeal to all the senses. In this poem, the shepherd woos his love by promising to provide what he believes would be appealing to her. In this regard then, he appeals to her senses of sight, touch, smell and hearing.
In stanza one the speaker promises that if the object of his affections should be with him and be his lover, they would be able to enjoy all the pleasures that nature, in all its forms, can provide:
... we will all the pleasures prove,
That Valleys, groves, hills, and fields,
Woods, or steepy mountain yields.
He is quite assertive and assures her that they will be able to definitely enjoy the sensuousness of nature. To further confirm this assertion, he uses the word prove - there will be no doubt that they are getting a thrill.
The second stanza continues in much the same vein, although the Shepherd becomes quite specific:
And we will sit upon the Rocks,Seeing the Shepherds feed their flocks,By shallow Rivers to whose fallsMelodious birds sing Madrigals.
In stanza three, the speaker appeals to his Love's senses of touch, sight and smell:
And I will make thee beds of RosesAnd a thousand fragrant posies,A cap of flowers, and a kirtleEmbroidered all with leaves of Myrtle;
A gown made of the finest wool andFair lined slippers for the cold,
Coral clasps and Amber studs
... dance and singFor thy delight each May-morning: