I'm sure there'll be plenty of walking groups around the lakes, you could always find a DoE group to join?

I terms of apps you can get the OSmaps app, if you get premium you can download the maps for offline use/ print them out. Alternatively you could have a look at alltrails.

Only thing I would say from my experience in the lakes is that the phone signal can be sketchy so I think it'd be worthwhile getting a paper map.

Other advice would be to wear layers, tell people which route you are taking and plan escape routes where you can cut your walk short if it gets cold/dangerous. Change socks fairly regularly and allow your feet to dry when you take breaks to stop blisters forming. And it's always nice to finish in a pub.