The information of Chinese Embassy in Kabul is given above in this page, you should apply for Chinese tourist visa at Chinese embassy in Kabul rather than at Afghanistan Embassy in Kabul. You need prepare the following documents and sumit them to the visa office of the embassy during their office:
1. Applicant's passport with blank pages and at least 6 months validity left before expiration.
2. A truly and completely filled application form affixed with one passport-sized photo.
3. Round-trip air ticket
4. Hotel reservation. Or proof of relationship in case of visiting relatives in china.
5.Other documents required by the visa officers if necessary.