French is a hard language. But here is a helpful way of learning the difference between à and a.
'a' is a conjugated form of the verb 'avoir'
e.g. il a un bateau (He has a boat)
'à' is commonly used as a preposition. Its meaning varies depending on the sentence. It can mean at, in, or to.
There is, however, a tricky rule. The preposition changes with the noun which follows it.
if the noun that follows the preposition is feminine: ... à la ferme (to/in/at the farm)
if the noun that follows the preposition is masculine: à + le = ... au bistrot (to/in/at the pub)
if the noun that follows the preposition is plurial: à + les = ... aux jeux (to/in/at the games)
When do I use à?
1. Introducing a location
e.g. Je vais à Londres (I am going to London)
e.g. Nous sommes allés aux toilettes (We went to the toilet) - Side Note: toilettes is plural in French
2. When talking about a point in time
e.g. Elle arrive à sept heures (She comes at seven o'clcock)
3. In terms of possession
e.g. C'est à moi (It is mine) - Side Note: à nous = ours / à eux = theirs ...etc
There are slightly more complex rules but these are the most used examples in the common French language.
Hope it helps.