How does the poet show in the poem "Lines Written in Early Spring" that objects of nature enjoy each other's company and are very happy?

Wordsworth mostly uses personification in order to show that flowers and other entities in nature are happy. Personification is the attribution of human qualities or feelings or actions to something that is not human. The speaker says,

And 'tis my faith that every flowerEnjoys the air it breathes.

Here, Wordsworth gives the flowers the ability to "enjoy" something, and because the thing that they enjoy is breathing the air, it sounds as though the flowers are simply happy to be alive. Further, the speaker states that "The birds around me hopped and played," personifying them by giving them the ability to play with one another, as if they truly do enjoy one another's company.
He also personifies the twigs on the trees, saying that they

[. . .] spread out their fan,To catch the breezy air;And I must think, do all I can,That there was pleasure there.

They are given the ability to spread out, to have purpose and intention, and the speaker believes that it gives the twigs pleasure to catch the breeze in this way.