The process of installing a template is extremely simple. You simply need to drag it into the Templates folder of your Unreal Engine version.
Blueprint versions of templates aren’t necessarily bound to a specific Unreal Engine version as long as the nodes are compatible.
<aside> ⚠️ However, C++ templates are bound to a specific version of Unreal Engine
</aside>
The default location for this is different for windows and mac.
Windows:
C:\Program Files\Epic Games\UE_[version]\Templates
Mac:
/Users/Shared/Epic Games/UE_[version]/Templates
https://lh7-us.googleusercontent.com/_lOrYsAlYI8HAUWUfYdNJb-KbEGFmgulTx4BaeXKLFxCS7-m6wFArLVG3yV97O39SRxYkdmdkAjBzqg3p02BykMxW4IiDoMQgfJlnLuq7vLwwYtyyRJza-DKp4WRgqBXfI4DxCZbcgR4DDKOSmviBbw
Once you’ve located this folder simply need to drag the TP_2DSideScrollerBP folder or the folder of whatever template you’re using in here.
Make sure that it’s an actual folder and not a .zip or .rar file. In that case you need to extract the folder first.
https://lh7-us.googleusercontent.com/4cp32nVuC8MYqHmaw3BB5CTVwE4rYKWo9MjeImx_50roGbRtXZtFfTciAaSqBNDvdVSX7VAb3D_nNpN4H9_RI98qD1h1ceG92vWOqYxGjUHBzGSKUWnTiHct2StfyJQwDuUf8KY5UTEv44kDVNsxZao
After doing that and opening up the new project browser of your Unreal Engine version, the template should then show up.
To add the template to multiple versions of unreal engine, just follow the previous steps and copy-paste it into the Template folder of all of your compatible Unreal Engine versions.
https://lh7-us.googleusercontent.com/1RGDYMtPDK3nqhQNohqb7CKv7f-RcUo7lLOxv9cTq6_J9nSu2anmRcHLb_7-ZCFPmqxm0fAI1TOuZvaDciucpPW5ufZKQdQS9KYUxyNNjGmTGAXLc8n_Vk8E23DHpwvZQbRPu7HHhlK7bD6heo0jNPM