Small cordless saws get forgiven for mistakes that would be obvious on a larger machine. The LCS1020 class is especially prone to two problems: the chain goes on backward because the cutters are tiny, and the tension is set with the bar nose hanging instead of lifted.
Open it carefully
Remove the battery first. Loosen the side cover and back the tension screw off enough that the bar can move inward. Brush chips away from the sprocket area and oil slot before you fit the new chain.
That close-up is the place to slow down. Tiny homeowner-saw hardware rewards patience more than force.
Direction and seating
On the top run of the bar, the cutter teeth must point toward the nose. Seat the chain around the drive sprocket first, then settle the drive links into the bar groove along the full length.
Tension the homeowner way
Reinstall the cover finger-tight, lift the bar nose, and then tension the chain until it sits against the underside of the bar without sagging. The chain should still pull by gloved hand. If you tension with the nose down, it will be looser than it looks once the saw starts running.
First-cut discipline
Add bar oil, make one short test cut in clean wood, then stop and recheck. A compact chain often settles after the first minute. That recheck is the difference between a clean install and an annoying mid-job adjustment.