Yup, please search and learn from the thousands of articles written on the subject of being a "first-timer" and logistical arrangements. Once you've recovered from that experience, feel free to ask any unique questions you may still have here.
Some of us, myself included, are notoriously long-winded on the forum and are willing to discuss anything. But, do narrow down the questions. Simply telling us, okay, I've decided to do this, now what do I do, is an very open question.
However, and because I cannot help being helpful... here is a start for you.
1. Fly into Paris from wherever you are. HOWEVER, if you are coming from the UK or the EU, disregard steps 1-3 here, as your transportation options are much better.
2. Take the "Les Cars du Air France" from the airports to Gare Montparnasse, Line #4 goes from CDG to the station (
http://en.lescarsairfrance.com/).
3. Book the TGV to Bayonne, the journey takes about 5.5 hours.
4. At Bayonne, switch to the TER (local) #62 tram / light rail shuttle to St. Jean Pied de Port on the next track. There was a mud-slide last year. They substituted buses for the trains while the line was repaired. I do not know the present status of the TER line. Others will certainly know.
5. Book one or two nights BEFORE you start walking in St. Jean to finalize packing, gear selection, and getting over jet lag (if pertinent). Also, St. Jean is a wonderful old town to explore. Start off by being a tourist for a day or two. You will be glad you did.
6. Once you KNOW the departure date from St. Jean Pied de Port, book your first night at Refuge Orisson. They book via e-mail. They DIO return messages, but it can take some time. Be patient.
If you have tourist stuff or extra gear you will need at Sanitago but not before, ship it to Sanitago using Express Bourricot (
http://www.expressbourricot.com/en/), or the poste. They are expensive, but ultra reliable and fast.
I hope this helps get you started...