Presidential appointees for cabinet and other key positions must get Senate approval. This has long been the case, and it's part of the Senate's job to offer "advice and consent" that is written into the Constitution.
But Trump is demanding that Republican leaders let him appoint whoever he wants, without a vote. This would let him unilaterally appoint the most extreme lunatics possible, without Senate approval. And it would let Senators avoid having to cast tough votes.
There is no way in hell the Senate should allow this to happen. Trump cannot be allowed to appoint unqualified and dangerous individuals to critically important positions.
Tell the Senate to do its job. Demand Trump get Senate approval for his appointments.