Dust off your old skills and prepare for new responsibilities.
把你荒疏已久的技艺重新练好，准备担负新任务。
《21世纪大英汉词典》
We must prepare a room for our guest.
我们必须为客人预备一个房间。
《新英汉大辞典》
prepare something=prepare for something这是在没人的情况下，
有人的时候就是prepare something for somebody为某人准备。。。
因为prepare既是及物动词又是不及物动词也就是既可以直接加名词也可以先加一个介词（一般和介词for连用）再加名词。不知明白否？
prepare
英 [pr?'pe?] 美 [pr?'p?r]
vt. 准备；使适合；装备；起草prepare something这是我添加的
vi. 预备；做好思想准备prepare for something这是我添加的
[ 过去式 prepared 过去分词 prepared 现在分词 preparing ]
柯林斯英汉双解大词典
prepare /prp/ CET4 TEM4 ( preparing, prepared, prepares )
1.
V-T If you prepare something, you make it ready for something that is going to happen. 准备
例：
Two technicians were preparing a videotape recording of last week's programme.
两名技师正在准备上周节目的录像。
例：
On average each report requires 1,000 hours to prepare.
平均每份报告需要1000个小时来准备。
2.V-T/V-I If you prepare for an event or action that will happen soon, you get yourself ready for it or make the necessary arrangements. (为…) 作准备; 准备 (做某事)
例：
The party leadership is using management consultants to help prepare for the next election.
该政党的领导层正聘用管理顾问来帮助准备下一次选举。
例：
He had to go back to his hotel and prepare to catch a train for New York.
他不得不回宾馆准备赶火车去纽约。
3.
V-T When you prepare food, you get it ready to be eaten, for example, by cooking it. 准备 (食物)
例：
She made her way to the kitchen, hoping to find someone preparing dinner.
她朝厨房走去，希望看到有人在准备晚餐。