before we learn how to play singed we need to learn what he does, his kit is built around being fast annoying and at the same time, tanky and strong. so lets go over his kit shall we?
https://leagueoflegends.fandom.com/wiki/Singed/LoL
this link will show you all the ins and outs of singeds kit, singes has great amount of tools to annoy his opponents, your q is for damage, farm and zoning, your w can be used to lock up a high priority target so you and you're team can focus him down. Your e is a versatile tool for engage, disengage and damage. And your ult is a big big part of your kit, both tank stats healing and mana regeneration as well as damage and anti heal all for 25 whole second which is more then enough to win a teamfight, a 1v1 or even a 1v2: the usual early game will be hard, get as much farm as you can because you need to get as much value as possible, either by killing the enemy, out farming him, proxying, getting plates or objectives. Make sure you are working with your team, by tping bot lane for a kill or 2, helping your jg with scuttle or helping mid get a kill. That is the general early game style that you want to do but in the mid game you get some nice options.

In the mid game you will have a couple of options: you can stay in lane push towers and get some nice farm and maybe some kills, this is good when you won early game and have a nice lead on your enemy laner. But what do you do when the enemy wins early game? Well then you need to sacrifice yourself to peel for your team, basically becoming a cc support but that builds some ap. this way you will snowball your team and get some nice gold yourself. But this both tactics can only go so far and the way to truly stand out is to combine them both. For example if you killed your enemy laner you can go ahead and roam to bot or mid and get a kill there meanwhile your laner is dead or coming to lane (assuming they dont have tp up). For another example lets say that drake is up, you should either tp there the second the fight breaks or try snd pressure the enemy laner to not go to the fight, you can even so both if you can kill the enemy laner then tp yourself, this way you will get amazing value by both having an extra man in drake fight and having the money from the kill. But in late game things get annoying for you.

The late game is an extremely difficult time for you, because most late game champ and carries will shred you in seconds, the trick is to not care about dying and just cc the hypercarries as much as possible. But when objectives come then it gets scary, you have to stop the enemy jg at all prices, even if it means you dying, baron and elder are extremely game changing and both can lead to an end in a couple of minutes. And now we will go to some nicer tactics to use when the time is right.

This tactic called proxying will be a great tool for you to win even the hardest of lanes if you do it properly. The first one is called proxying. This statagy will let you dominate the wave state with relative ease. You need to go behind the enemy’s first tower(you can go behind the second one but this is riskier), you tank the minions yourself and farm them with q, Of course this takes alot of health so i usually go fot curropting potions and time warp tunic for the health and regen and i go for minion demetirializer and if a hard time go for biscuits delivery for the even more health and mana regen. But just a quick reminder, make sure you have proper vision of the enemy jg, because if he comes into the equation its 99% a death for you. So WARD ALOT.

well i am out of things to tell you but i recommend you go to the minishcap youtube and twitch channel because he makes alot of guides and says alot of nice tips in his videos and streams.
https://www.youtube.com/channel/UC6hA1jzh5eUdUngDIRk0cDw
https://www.twitch.tv/minishcap1
i am not working for this man so this isnt a biased opinions its just my preference, and i want to recommend a man who can give you alot of tips some are better then mine by 10 fold. good luck on the rift out there singed players and remember, if ur toxic screw you!