Meeting new people in a new place is difficult when they speak the same language. When they speak a foreign language it is much harder. Language is discussed elsewhere but is key to the whole problem of meeting new people.
Many people arrive in France newly-retired, and rapidly become part of the expat community, and never look back - and frequently never learn to speak French.
You will usually not need to search too hard to find this community - they will find you! If that is the community you wish to be part of (and nothing wrong with that) all should be straightforward, unless you live somewhere completely isolated.
It is being accepted by the French community that is harder. A typical rural community has many families who have lived in the same town or village for generations, who all went to school together and now work together, and realistically you can only be peripheral to that society for several years.
That is not to say it isn't worth making an effort, because if you don't you will never fit in, but it can be a long and hard process.
First, learn your French manners. Always say 'bonjour monsieur', 'bonjour madame' to everyone you pass who catches your eye, and smile. Comes hard at first to be so forward, but now it seems very strange when I meet English people who don't do the same - it seems quite unnatural to walk passed someone in the street without a quick exchange. If you don't you are being 'rude and offish'.
Some people are fortunate enough to find they have the perfect French neighbour, who is always dropping in offering advice, and always to hand. If you are one of these people, return the compliment because you are very lucky. This is much the easiest way to become accepted, and also to learn French.
In any case, don't be discouraged, it gets easier with time.
The whole point of this really is to explain that it is slow and difficult to become established in a small French community (and to be honest, in many communities you will still be an 'outsider' after 20 years), and not to be deterred if progress seems slow, because it will get easier. Just don't expect miracles.
An introduction: Living in France
Financial considerations: Finances of moving to France
Moving on a limited budget / how little money can you move with: Relocating on a budget
Language considerations: problems with learning the language: Language problems for expats
Meeting people and becoming established: living in a French community
Schools and education: expat children in French schools