कथं विद्यामहं योगिंस्त्वां सदा परिचिन्तयन्। केषु केषु च भावेषु चिन्त्योऽसि भगवन्मया ॥

kathaṁ vidyām ahaṁ yogins tvāṁ sadā parichintayan keṣhu keṣhu cha bhāveṣhu chintyo ’si bhagavan mayā

How may I know thee, O Yogi, by constant meditation? In what, in what aspects art Thou to be thought of by me, O blessed Lord?

In plain words: Arjuna asks Krishna how he can come to know Him by always thinking of Him. He wants to know in what forms or things he should think of Krishna.