There are a number of things to consume and do which might help with your appetite, but I think the first thing to address is the fact that "poor apetite" itself is not a physical disorder. Poor appetite usually stems from some other condition, especially emotional factors which may accompany stress, depression, illness, trauma, etc. Alchohol use and smoking can also reduce the appetite. And there may be underlying undetected problems such as heavy metal poisoning and/or nutritional deficiencies.
Often, people who have underlying problems and used appetite stimulators wish they had not done so once the underlying problems are addressed - the long term result may be overeating instead!
Do you smoke? If so, stop! How about drinking? If so, stop or cut way back.
Once you have taken a good look at the possible underlying problems and addressed those, if you still wish to increase your appetite, some things which may help are:
To stimulate an apetite, meals must be tailored to individual taste and tolerance. Perhaps you should try smaller portions and meals throughout the day and/or healthy snacks (bananas, avocados, cheese, chicken, fruit shakes, turkey, yogurt, nuts, seeds) may be better and more appetizing than the site of big meals.
Exercise can help, but do not do so strenuously.
And again, first look for other underlying causes. Once you correct those, appetite may not be an issue.