Purport

Now Bhagavan Shri Krishna gives the third way to approach devotion to Shri Krishna. First, two approaches were to align mind and intelligence onto Shri Krishna using meditation and continuous efforts to all the methods like reading, rituals, listening to masters of yoga, etc. But for some reason, if a human cannot practice the path of yoga and achieve the enlightened state of mediation, he still does not have the reason to lose.

Bhagvan Shri Krishna now suggests you your duties to the best of your skills and capabilities but do your activities as if you are offering your very actions to me and dedicating your actions to me.

In this way even if you are incapable of practicing yoga or the art of devotion, or fail even to indulge in devotional activities, you can still achieve the same state of perfection of devotion by simply doing your acts considering as the service to Shri Krishna.
By this method, anybody can achieve the highest state of the devotional state, if he just has faith in Shri Krishna and does his duties as a service to Shri Krishna.

if we go more into spiritual details and try to understand the whole mechanism. The above method though very simply involves one of the most subtle concepts of Sanatan Dharma. In Chapter 6, chapter 10 and many other places, Bhgvan Shri Krishna has explained that He is present in every living being and one who sees Shri Krishna in every living being is actually very close to Shri Krishna,

yo māṃ paśyati sarvatra sarvaṃ ca mayi paśyati |
tasyāhaṃ na praṇaśyāmi sa ca me na praṇaśyati || 30 ||
One who always sees Me everywhere and sees everything in me, I am never out of sight for him, and he never out the sight of me.
--Ch6:Sh30

Therefore any human being if serving any living being is actually serving Shri Krishna.