welcome to the forum !
it's clear from your profile the reason you want to lose weight and get fit .
So motivation shouldn't be a problem now you've decided to take the bull by the horns as it were.
You're absolutely doing the right thing by walking before you can run .
I don't know when you last exercised so it's a little difficult to say about distances ,but assuming you have'nt done any then you need too start of with a short distance of say a mile
Try to walk briskly so that you are breathing a bit harder ,if you have any unusual pains or any tightening in your chest naturally stop.If all goes well in the first couple of weeks then gradually increase the distance you walk by no more than 10%
After about three weeks to a month all is going well it might be time to start to think abouty preparing yourself for a gentle SHORT! run do what you feel comfortable with but about a mile should be ok Don't go mad though gradual build up is the key to meaningful,pain free and injury free running.
you'll find a lot of support on the forum
take it easy ,let us know how you are progressing because it's people like your goodself that can be the inspiration to others!!!
good luck
