OK. Simple advice first, take it steady and work well within your limits when first starting out. If you follow this advice you will be the exception to the common rule of people trying to undo five years in as many days, and several times more likely to succeed.
Do some very steady running or cycling, with easy breathing and good focus on technique. Take note of your distances and times for comparison in a few months only, do not look for dramatic improvement in the first few weeks, it may come but you shouldn't seek it.
Progress should be that the activities become easier and you are making them part of your life. Speed increase etc. should come after you have got technique right and are comfortable with what you are doing.
Most important. Enjoy it, if you don't you are far more likely to quit. This means not overdoing it so you feel dead or wish you were at the end and the day after. Wait until you love it to aim for that.
