Aymen,
By default, the TSLint validation is turned on for projects if tslint.json is present.
You can check if the validation is enabled or not here : Right click on the project > Properties > TypeScript > TSLint.
To check if the project is using the correct tslint.json, select TypeScript and check if the path for tsconfig.json is pointing to the right tsconfig.app.json file. You can customize TS code formatting in the TypeScript > Formatter page.
If you are seeing any specific issues related to TS formatter and validation w.r.t tslint.json, then please elaborate the exact problems you are seeing. Please share with us code snippet and screenshots of the issue to help us investigate further.
–Swapna
MyEclipse Support