Just go to Akara after you've completed that and you'll get a free respec.

There are three free respecs, one per difficulty level after completing the Act 1 'Den of Evil' quest in Normal, Nightmare, and Hell. One of the more daunting things to me about D2 always was the 'You can only do it once' part of the builds. That's pretty dope, hope they don't remove/ban that. We've prepared a Skill Reset Guide which explains how to Reset your Skills for each difficulty and the Horadric Cube recipe to transmute a Tome of Absolution. Once you've run out of those, your only option is to farm a Skill Reset from Hell difficulty, using a very rare combination of items. In Online Play, this launch command won't have any effect and you will still have a limited number of 'free' skill resets. Below is an image of what the game settings should look like in your Battle.Net launcher to enable free skill resets. Once clicked, select 'Game Settings', enable 'Additional command line arguments', and type in '-enablerespec'.

To get to the Game Settings page, click on the cogwheel next to the Play button on your Diablo II: Resurrected page in the Battle.Net launcher. This process involves opening the game settings in the Battle.Net launcher and adding '-enablerespec' in the command line argument, which will allow you to freely reset skills from the character stats page.

In Diablo II: Resurrected Offline Play for PC, community member Raxxanterax shared a YouTube video showing how to enable free skill resets.

Diablo 2 respec cheat