The Greek word translated as "sent" in Mark 1:12 is "ekballo," a word which means to cast out or throw out. The word has a connotation of violent compulsion; the same Greek word is used in John 2:15 to describe Jesus' act of driving the sheep and oxen out of the temple area. It's not easy to imagine the Holy Spirit driving Jesus into the desert to be tested.
However, look at the interaction between Jesus and the Holy Spirit which occurred just prior to this. The Holy Spirit had been sent from the Father to descend on Jesus like a dove. The Father told Jesus that He was His beloved, favored Son (Mk 1:11). Before the Spirit threw Jesus out into the desert, He rested on Jesus and assured Him of the Father's special love.
If the Holy Spirit, Who is Lord (2 Cor 3:17-18), can drive Jesus into the desert to battle Satan, He will certainly drive us into battle, for we are disciples of Jesus. During the heat of the spiritual battles, temptations, and testing of Lent, we must always remember that first the Holy Spirit is poured out in our hearts so we will know God's love (Rm 5:5) and be confirmed in it (2 Cor 1:21-22).
If Jesus goes into the Lenten desert, so do we. We follow in His steps (Lk 9:23) toward every test God has for us. "No test has been sent" to us that hasn't come to Jesus or others (1 Cor 10:13). The Spirit "will not let [us] be tested beyond [our] strength " (1 Cor 10:13). Therefore, "let us follow the Spirit's lead" (Gal 5:25) and His drivings.