There realy are configuration docs on the cisco web site, but assuming your pix is setup to pass traffic already, ie; you have the statics, routes, and nat statements in place, adding acls is pretty easy.
access-list outside permit tcp host 1.1.1.1 host 2.2.2.2 eq any
This will let 1.1.1.1 do any tcp connection to 2.2.2.2
of cours, you have to apply the access list to a group, but we dont have room for all that here, like i said, if it is setup to pass traffic already and you just want to add a new rule, that is the format. If you use host, you dont need a mask, if you want to allow a subnet, it is 1.1.1.0 255.255.255.0 sort of a format. Version 6.3 allows you to build groups of services and networks and use them in rules, which saves a lot of typing.
Good luck