Update readme

README.md

@@ -1,6 +1,11 @@
 # Header Chain Proof
 A STARK proof of Bitcoin's header chain
 
+Remember to activate the Python environment into which you've [installed Cairo](https://www.cairo-lang.org/getting-started/)
+```
+source ~/cairo_venv/bin/activate
+```
+
 
 ## Run Tests
 ```sh
@@ -23,7 +28,7 @@ make batch_proof BATCH_SIZE=63 BATCH_NUMBER=0
 ```
 
 ### Aggregate Proof
-This command aggregates two batch proofs (or aggregate proofs) into a single, aggegated proof.
+This command aggregates two batch proofs (or aggregate proofs) into a single, aggregated proof.
 
 ```sh
 make aggregate_proof PREV_PROOF=batch_proofs/batch_0 NEXT_PROOF=batch_proofs/batch_1 START=0 END=125 
@@ -41,3 +46,5 @@ make increment_proof BATCH_SIZE=63 START=0 END=62 PREV_PROOF=batch_proofs/batch_
 ```sh
 make batch_program_hash
 ```
+
+