You'll have to tell us what connections / cables you have in the switches.
But basically you have to disconnect the 'strappers' going between the switches, re arrange the original switch so your feed is on C, and your swith live is on L1. You will probably have three cables connected (3 cores, 1 cable) connected to C, L1, L2 you need to disconnect these and secure them. This is at BOTH switches. OR it may be wired two plate where there is a two-core cable running between the switches, this is the same procedure and needs disconnecting at both ends again, securely.
The single cabe feeding the light (The switch live) also needs securely disconnecting.
Then its a 1.5 Twin & earth between light fittings connecting the Switch lives, netrals and earths. You may want to take the loop over too just to have there for the future.
Theres plenty of advice in the forums advice pages.