Just build up slowly. Legs take a proper pounding when running that they won’t be use to from cycling. Things like tendinitis can easily crop up when you start running if you have strong leg muscles from cycling. Can have issues caused by muscle imbalance too.
No more than 5% increase a week seems to be a general rule of thumb, though make sure you listen to any aches and pains.
When I’ve had a long time off running with injury, I find I really have to hold back when running. Fitness due to cycling would allow for a lot more but it’s a quick way to pick up another injury.
As for barefoot running, get a good book on it. You need to go very slowly if you are giving that a try. Most seem to recommend a month just doing walks around the house, then a month building up walking outside, then a month trail walking, then even more time on short runs… you get the idea.
Hope this didn’t sound all doom and gloom, but I love my running and not being able to run due to injury totally sucks. Hope you get on ok.
Oh just remembered I read an article a while back from Chris Carmichael about Lance training for the marathon and the issues of cyclists transitioning to running. Might be able to google it.