Hi Rashmi, 
Welcome to HCM.
It is unfortunate to note that your father has landed up in cirrhosis of liver. 
It is a liver disorder which is associated with 
weight loss. It also decreases appetite, which will add on to his weight loss. 
Since in this condition, albumin is not synthesised in the liver, there is a severe protein deficiency. 
To increase his appetite, you can give him 
digestive enzyme  syrup preparations. For diet, give him easily digestible simple 
carbohydrate rich sift diet. 
You should provide 
protein supplements in powder form with milk daily along with white portion of boiled egg. This will supplement protein and help him to gain weight. 
Take care to also provide 
multivitamin and mineral capsules regularly. 
If he is a smoker and alcoholic, he needs to stop it completely as it will worsen his condition. 
Hope the information provided would be useful. 
Take care and All the best.