Tā jìn le dà gōngsī, dàshù dǐxia hǎo chéngliáng ma.
He got a job at a big company: there is good shade under a big tree.
Tips
usage
乘 means "to make use of" here, not "to ride". The saying can be plain advice or a dig at someone living off connections. Compare 前人栽树,后人乘凉 "earlier generations plant the trees, later ones enjoy the shade", about benefiting from others' work.