Once you get an appointment for the GU (German for General Untersuchung -> General Examination(s), since you have a licence, you then refered to as Ready-Entry) they send you all the information in an email with links to various files. If you download all the files, somewhere in there one called EW Berwerbungsprozess. This details the steps that you can look forward to
. Everything is explained to you beforehand so really no need to stress right now. I still do not recommend getting Skytest, but if it makes you feel better, get it and kill some time between applying for other airlines.