Manual for SNP calling for soapsnp

Question

[lakhujanivijay]

Can somebody provide the manual/steps for SNP calling using soapsnp? I went through below link

http://soap.genomics.org.cn/soapsnp.html#insta2

1. Required parameters: -i <file> Input SORTED SOAP alignment result Note that here we say “sorted’ means alignments of each chromosome are sorted first by chromosome name lexicographically and then by coordinates on each chromosome numerically.

I could not understand what is SORTED SOAP alignment means here and how could I achieve the same? Does that mean I have to first align the reads on reference and then use the sorted BAM file in SOAPSNP?

I am just exploring the tool and trying to find out how it works.