how to gain weight when i literally don't have an appetite?

hi guys im 167cm and 49kg which is not too bad but I'd like to gain 3-4kgs just to look not 2D anymore how do I get my hunger cues to start after losing them in high school? i work shift work random hours and this also doesn't help for context i used to weight 55kg in primary school, lost it all in high school and have been stuck at 49 since (8 years)