The foundation plan is the start of your triathlon journey, around 6 - 12 weeks duration and roughly 30 - 36 weeks out from your major race. That said, if your swim is front pac & does not need work, you can start putting in "winter" training on your swim (harder sessions). However, if you are new to running and your run needs a lot of technical work to improve your economy, thus slower progressions. You may need to stay in the "foundation phase" for longer than 12 weeks to ensure you are technically sound and don't get injured.
This phase will equip you with the tools necessary to cope with the harder winter to follow. You will see that the sessions are laid out with a flow to them. Of course not everyone can do the swim on a monday morning, however with your weeks training try to follow a few guidelines:
1. As much as possible have one rest day per week (mental & physical freshening up)
2. It is ok to move sessions around, but try to give 48hrs of easy or drill work between harder sessions
3. If you are training in the am fasted (without food) try to make this session easy to utilise fat adaptation (burning fat stored in the body)
4. Week 4 is a "freshening-up" week, this does not mean do nothing, but things like having sunday am off with be great news for your partner and for you to have breakfast in bed! You still have to nail the key sessions.
5. Don't do two run sessions consecutively, unless your body is robust enough to handle this
6. Don't be in a rush to be super fit and training really hard during this phase, I have seen many an athlete elite and age group burnt out or injured three months into their new programme. Keen is great, but put that enthusiasm into becoming economical and a little fitter.
Improve technique = improved economy & less injuries = consistent athlete