I don't think it's routine like it is to teach parents how to care for central lines, but they'll probably train you if you ask (especially if home IV meds/fluids/TPN are going to be involved). The clinical nurse specialist for the oncology unit showed me and DH how to do it.
Your home health company will send you all the supplies you need (with orders from your child's doc). In the hospital they have premade kits that come with everything all sterile and ready to go, but our home health company doesn't do port access kits so I have to tell them what I need. I get all the supplies I'll need to access J for the month, then I make my own little kits and put everything together in ziploc bags. If you're not on a certain protocol for home infusion, you can probably ask for enough supplies for 2 or 3 accesses, just to have on-hand. Plus whenever you're in the hospital you can use their supplies.