The map below is of the town of Garlsdon. A new supermarket (S) is planned for the town. The map shows two possible sites for the supermarket.

(From Cambridge IELTS 5)
Here is some advice:
1.Introduction– Just paraphrase the question (instead of ‘two possible sites’ you could write ‘two potential locations’).
2.Summary– The main point is that the first site (S1) is outside the town, whereas the second site is in the town centre. Also, you could mention that the map shows the position of both sites relative to a railway and three roads which lead to three smaller towns.
3.Details (2 paragraphs) – Don’t write a separate paragraph about each site; it’s much better to compare the sites. I’d write one paragraph comparing the position of each site relative to Garlsdon (mention the different areas of the town), and another paragraph about the positions relative to transport links with the other three towns.

The map shows two potential locations (S1 and S2) for a new supermarket in a town called Garlsdon.

The main difference between the two sites is that S1 is outside the town, whereas S2 is in the town centre. The sites can also be compared in terms of access by road or rail, and their positions relative to three smaller towns.

Looking at the information in more detail, S1 is in the countryside to the north west of Garlsdon, but it is close to the residential area of the town. S2 is also close to the housing area, which surrounds the town centre.

There are main roads from Hindon, Bransdon and Cransdon to Garlsdon town centre, but this is a no traffic zone, so there would be no access to S2 by car. By contrast, S1 lies on the main road to Hindon, but it would be more difficult to reach from Bransdon and Cransdon. Both supermarket sites are close to the railway that runs through Garlsdon from Hindon to Cransdon.

potential adj [ before noun ] UK ​/pəˈten.ʃəl/ US ​/poʊˈten.ʃəl/
centre noun [ C ] uk us center UK /ˈsen.tər/ US /ˈsen.t̬ɚ/